CN101213461B

CN101213461B - Methods and systems for detecting a capacitance using SIGMA-DELTA measurement techniques

Info

Publication number: CN101213461B
Application number: CN200680019492.2A
Authority: CN
Inventors: J·K·雷诺; K·哈格里夫斯; D·埃利; P·鲁特利; A·多伊格; J·海恩斯
Original assignee: Synaptics Inc
Current assignee: Synaptics Inc
Priority date: 2005-06-03
Filing date: 2006-06-02
Publication date: 2013-01-02
Anticipated expiration: 2026-06-02
Also published as: CN101273274A; CN101213461A; CN101283507A; CN101283507B

Abstract

Methods, systems and devices are described for detecting a measurable capacitance (Cx) using sigma-delta measurement techniques. According to various embodiments, a voltage is applied to the measurable capacitance (Cx) using a first switch. The measurable capacitance is allowed to share charge with a passive network. If the charge on the passive network (109) is past a threshold value, then the charge on the passive network (109) is changed by a known amount for a sufficient number of repetitions until the measurable capacitance (Cx) can be detected. Such a detection scheme may be readily implemented using conventional components, and can be particularly useful in sensing the position of a finger, stylus or other object with respect to a button, slider, touchpad or other input sensor.

Description

Use the method and system of SIGMA-DELTA measuring technique Detection capacitance

Right of priority

[0001] the application requires the U.S. Provisional Patent Application No.60/687 of submission on June 3rd, 2005,012,60/687,166,60/687,148,60/687,167,60/687,039 and 60/687,037 reach the No.60/774 that submits on February 16th, 2006,843 right of priority, they are introduced into as a reference at this.

Technical field

[0002] the present invention relates generally to capacitance detecting, relate more specifically to use SIGMA-DELTA type measuring technique can detect equipment, the system and method that to measure electric capacity.

Background technology

[0003] capacitive transducer that electric charge, curtage is occured to respond can or close on for detection of the position (perhaps motion or existence or any similar information), and the input equipment that is typically used as computing machine, personal digital assistant (PDA), media player, video game machine, consumption electronic product, cell phone, coin telephone, point of sales terminal, automatic speaking machine, call box etc.In user's load button, slip control, rolling ring, rolling band and other type sensor, use capacitive transducer.One of employed capacitive transducer type is the button-type sensor in this application, and it can be used for providing the information that occurs or exist about input.The another kind of type of employed capacitive transducer is the touch-pad type sensor in this application, it can be used for providing the information about input, such as position, motion and/or along the similar information of an axle (1-D sensor), diaxon (2-D sensor) or multiaxis.Button-type and touch-pad type sensor also selectively are configured to provide other information, some indications of the acting force that for example is associated with input, duration or capacitive coupling amount.In U.S. Patent No. 5,880, an example based on the 2-D touch-pad type sensor of capacitance detecting technology has been described in 411, this patent licenses to Gillespie etc. on March 9th, 1999.For example, this sensor can easily find in the input equipment of electronic system, and this electronic system comprises hand-held and notebook computer.

[0004] usually, the user is usually by placing one or more finger, contact pilotage and/or object or mobile near being arranged on the input equipment or the sensitive zones of one or more sensors of input equipment comes the operation of capacitor input equipment.This is in application on the carrier signal of sensitive zones and produces capacity effect, described carrier signal can be detected and with stimulate/excitation is associated with respect to the positional information of sensitive zones (for example position or close on or motion or existence or similar information).Next, this positional information can be used for selecting, move, roll or operates in text on the display screen, figure, cursor and the highlighted and/or any combination in any of other designator.This positional information also can be used to make user and interface alternation effect, for example controls volume, adjusts brightness or realizes arbitrarily other purpose.

[0005] although capacitive transducer has been widely used for many years, the sensor designer continues to seek the method that improves sensor function and efficient.Particularly, the slip-stick artist is not in the situation that increase the design and implementation scheme that cost makes great efforts to simplify position transducer unceasingly.In addition, because day by day increase in the demand of all kinds electronic equipment to this sensor, so occurred the high flexibility demand of sensor design scheme low-cost and that easily implement again.Particularly, occurred dirigibility is enough to be used in various embodiments and has enough abilities that the simultaneously needs of the sensor design scheme of retained costs benefit of accurate capacitance detecting are provided.

[0006] therefore, be desirable to provide fast, effectively and efficient detection can measure the system and method for electric capacity.In addition, wish to create a kind of the use and hold the design proposal that facile element can easily be implemented, the facile element of described appearance is IC standard, microcontroller and discrete elements for example.According to detailed subsequently instructions and appended sharp claim, with aforementioned technical field and background, the characteristics of other hope and characteristic will become apparent by reference to the accompanying drawings.

Summary of the invention

[0007] describe use SIGMA-DELTA measuring technique for detection of the method that can measure electric capacity, system and equipment, described SIGMA-DELTA measuring technique need not to require inner active analog element just can carry out on many standard microcontrollers.According to various embodiment, use the first switch to apply voltage to measuring electric capacity.Permission can be measured electric capacity and be shared electric charge with passive network.If the electric charge on the passive network surpasses threshold value, then the electric charge on the passive network is changed scheduled volume, and repeats this process.The result that charge threshold detects is the measures of quantization to electric charge, can carry out filtering to produce the measured value of measurable electric capacity to it.This detection scheme can use and hold facile element and easily enforcement, and can specifically be applied in and detect finger, contact pilotage or other object with respect to the position of capacitive transducer, this capacitive transducer executive button function, sliding function, cursor control or user interface navigation function or any other function.

Description of drawings

[0008] below, in conjunction with accompanying drawing subsequently various aspects of the present invention will be described, same numeral same parts wherein, and

[0009] Figure 1A shows the block diagram of typical first order SIGMA-DELTA detection technique, and Figure 1B is the typical sequential chart of embodiment shown in Figure 1A;

[0010] Fig. 2 is the process flow diagram of typical SIGMA-DELTA capacitance detecting technology;

[0011] Fig. 3 A-B is typical SIGMA-DELTA capacitive detection circuit figure, and its three digital incoming/outgoing pin with passive network and controller realize, Fig. 3 C is typical time-scale, and Fig. 3 D is the typical sequential chart of exemplary embodiments shown in Fig. 3 A;

[0012] Fig. 4 A-B is typical SIGMA-DELTA capacitive detection circuit figure, and its two digital incoming/outgoing pin with passive network and controller realize, Fig. 4 C is typical time-scale, and Fig. 4 D is the typical sequential chart of embodiment shown in Fig. 4 A;

[0013] Fig. 5 A is typical SIGMA-DELTA capacitive detection circuit figure, and its digital incoming/outgoing pin with passive network and controller realizes, Fig. 5 B is typical time-scale, and Fig. 5 C is the typical sequential chart of embodiment shown in Fig. 5 A;

[0014] Fig. 6 A-B is replaceable typical SIGMA-DELTA capacitive detection circuit figure, and its I/O pin with passive network and digitial controller is implemented many sense channels;

[0015] Fig. 7 A is typical multielectrode sensor figure, and it is included in the DELTA capacitor of sharing between the sense channel, and Fig. 7 B is the status switch table of being correlated with;

[0016] Fig. 8 A is that the typical case that uses the SIGMA-DELTA technology to implement connects and changes electric capacity (transcapacitive) sensor figure, and Fig. 8 B is the status switch table of being correlated with, Fig. 8 C is the parallel transformation of the typical case capacitive transducer figure that uses the SIGMA-DELTA technology to realize, and Fig. 8 D is the status switch table of being correlated with;

[0017] Fig. 9 A-B is for the circuit diagram that reduces the representative configuration of power supply noise impact at capacitive detection system; With

[0018] Figure 10 is the schematic diagram with approaching sensor equipment of electronic system.

Embodiment

[0019] detailed instructions in fact only is exemplary below, and is not used in restriction the present invention or the application and use of the present invention.In addition, intention do not lie in by aforementioned technical field, background, brief overview or below theoretical constraint the expressed or that imply in the detail specifications.

[0020] according to various exemplary embodiments, use the SIGMA-DELTA modulation technique can easily make up capacitance detecting and/or metering circuit.Usually, term " SIGMA-DELTA " relates to the simulation digital transition scheme extremely that quantizes electrical effect (for example electric capacity) in conjunction with electric charge summation (SIGMA) and differential (DELTA), and described electrical effect is showed by electrode or other electrical nodes.In the SIGMA-DELTA capacitance detecting, for example, analogue integrator usually accumulation shifts the electric charge of coming according to a plurality of electric charge failover events from measuring electric capacity.Also be applied in the other electric charge that has relative signs from measuring electric charge that electric capacity receives and preset the quantity, to keep near near the electric charge that gathers the known level.Namely, from analogue integrator, extract suitably the electric charge of quantized amount, to keep the wave filter output near ideal level.The quantity that is used for the relative electric charge of integrator by association can be determined the quantity of electric charge that shifts by measuring electric capacity.Next, can use this capacitance to confirm finger, contact pilotage or other objects near the appearance of institute's detection node or do not occur, and/or be used for arbitrarily other purpose.Therefore, the SIGMA-DELTA scheme can be used in many distinct methods, to determine the electric capacity on present electrode or the analog.

[0021] in addition, (for example only use conventional trnasistion mechanism, the signal pin of opertaing device, discrete switch etc.), just easily realize following various embodiment, the input of numeric door need not to increase the extra active electronic equipment of cost and complexity as quantizer (it can also use the signal pin of opertaing device to be implemented) and passive element (for example one or more capacitors, resistance and/or analog).Therefore, use easily to obtain and the reasonable element of price, can conveniently in various environment, implement reliably again various schemes described here, as described more fully below.

[0022] turns to now accompanying drawing and beginning with reference to Figure 1A, be used for determining to measure capacitor (C _X) 102 typical first order SIGMA-DELTA converter 100 comprises passive network 109, quantizer 110 (if it can be comparer or expect that then it is the input of numeric door to a quantizer), digital to analog converter 116 (it can be the switch to one or more voltage) and be used for allowing to measure electric capacity 102 and DELTA " reference " electric capacity (C _D) 126 suitably to the switch 106,122 of the suitable quantity of integrating capacitor 108 charging and dischargings.

[0023] in this embodiment, passive network 109 is embodied as integrating capacitor 108 simply.Shown integrating capacitor 108 (C _I) utilize conventional capacitor to realize, described conventional capacitor is configured to usually have the incomplete integrator of larger capacitance values, and the desired numerical value that described capacitance maybe can be measured electric capacity 102 than the numerical value of DELTA electric capacity 126 usually is large (for example, greatly one or more order of magnitude) obviously.In each embodiment, for example, but measure electric capacity 102 and DELTA electric capacity 126 can be the picofarad level, and integrating capacitor 108 is the bicrofarad level, although other embodiment can be broadly in conjunction with the different numerical value that are used for specific capacitor.In conjunction with digital to analog converter voltage 118,120 and charging voltage 104, effectively DELTA electric capacity 126 determines to measure the scopes of capacitance values.Also possibly put upside down the electric capacity measured 102 among Fig. 1 and the role of DELTA electric capacity 126.In this case, will be transferred to integrating capacitor 108 to electric charge from DELTA electric capacity 126 by switch 106, and can to measure electric capacity 102 can be feedback capacity, this feedback capacity is shifted by switch 122 and by data 114 controls.This causes data output 114 and can measure electric capacity 102 inversely proportional, and is in direct ratio with DELTA electric capacity 126.Wherein in reciprocal mechanism, determine or the embodiment of signal that filtering occurs or noise in, this " reciprocal electric capacity " sensor is useful with respect to the direct proportion capacitive transducer.

[0024] can measure electric capacity 102 is the effective capacitances that have by any signal source, electrode or other electrical nodes of SIGMA-DELTA converter 100 detectable electron capacitance.In Figure 1A, can measure electric capacity 102 and be shown as variable condenser.For the input equipment of accepting input from one or more fingers, contact pilotage and/or other excitation (stimuli), can measure often total effective capacitance (" absolute capacitance ") of the local ground connection of expression from detection node to system of electric capacity 102.The total effective capacitance that is used for input equipment can be very complex, relates to such as electric capacity, resistance and inductance by sensor design and the determined series and parallel connections of operating environment.In other situation, can measure electric capacity 102 and can represent from driving node to total effective capacitance (" transformation electric capacity ") of detection node.The all right very complex of this total effective capacitance.Yet, in many cases, can be the small variable capacitance with the fixed background Capacitance parallel connection with the input simple analog.In any situation, impose at first with reference to the charging voltage 104 of local system ground connection and can measure electric capacity 102, as following more abundant described, then allow to measure electric capacity 102 and share the electric charge that produces by applying charging voltage 104 with passive network 109.

[0025] in the typical SIGMA-DELTA converter 100 shown in Figure 1A, can measure electric capacity 102 and be charged to charging voltage 104, and share electric charge in response to the position of switch 106 with integrating capacitor 108.Similarly, DELTA electric capacity 126 is charged to appropriate value (for example, low reference voltage 118 described below or high reference voltage 120), and is applied to integrating capacitor 108 via switch 122.Switch 106,122 responsive control signals 105,124 are set to respectively proper states, and described control signal 105,124 is for being suitable for switch 106,122 is set between when appropriate any electricity, logic or other signal of proper states.In various embodiments, switch 106, the 122 input/output signal pins by digital control circuit provide, the internal control signal that produces in control circuit of response and control suitably this input/output signal pin.In the simple concept embodiment shown in Fig. 1, control signal 105,124 is by symbol φ ₁, φ ₂Indicate.These control signals can be periodicity, acyclic, produce by steering logic and/or analog.In various embodiments, DELTA electric capacity 126 can be recharged and share to integrating capacitor 108 continuously for several times.This embodiment will allow relatively little DELTA electric capacity 126 to play very large effective capacitance effect.Namely, the actual change (or " DELTA ") that imposes on the electric charge of integrating capacitor 108 is the numerical value by DELTA electric capacity 126 but also determine by the concrete steering logic that applies via switch 122 and the numerical value of reference voltage not only.

[0026] use any quantization device 110 or other simulation to numeral to change (ADC) technology, the electric charge that remains on the integrating capacitor 108 is converted into numeric data stream 114 suitably.In various embodiments, the input of simple comparator or numeric door provides an ADC output, and whether the input voltage of its indication integrating capacitor 108 is greater than or less than reference voltage (V _Cmp) 112.An ADC output is latched by control signal subsequently, for example the signal psi shown in Figure 1A-B ₁Although the simple examples quantizer 110 shown in Figure 1A provides logic " height " or " 1 " output when integrating capacitor voltage surpasses reference voltage 112, this transformation is elective to a certain extent; Therefore, in the situation of theory described here, alternative embodiment may provide logic " low " or " 0 " output under this situation.Can sample to the output that comes quantizer 110 with any usual manner (for example, using digital latch circuit 111), to keep for the data stream 114 with aftertreatment.

[0027] expression of output data 114 can be stored by any way, filtering (for example, by digital filter 115), average, extract and/or any digital output set of other processing.Use many threshold values, stacked ADC level and/or use routine techniques etc., other embodiment can provide multidigit resolution.For example, can pass through more than a reference voltage (for example, a plurality of comparative voltage V _Cmp) threshold value is provided.This high-resolution output can be latched at one and constantly locate or be latched as a series of outputs (for example, as approaching one by one).Can also use the digit data stream 114 that provides by quantizer 110 and/or latch 111, with definite " DELTA " electric charge (same " ladder " electric charge) that will impose on the suitable quantity of integrating capacitor 108.A plurality of DELTA electric capacity same or different sizes can also be used for changing the quantity that applies electric charge.In the exemplary embodiments shown in Figure 1A, for example, the voltage on logic high (" 1 ") the output 114 expression integrating capacitors 108 exceeds the situation of reference voltage 112, and indication should apply corresponding " DELTA " electric charge by DELTA electric capacity 126.Therefore, data output 114 can be used for selecting between " low " and " height " reference voltage 118,120, perhaps the quantized values of some between them changes (DAC) 116 so that simple digital to the simulation of controlling the electric charge that is applied by DELTA electric capacity 126 to be provided.Replacedly, whether the electric charge (being reference charge) that can control on the DELTA electric capacity 126 of one or more data output 114 shares (arbitrary portion of for example, transferring to this integrating capacitor 108) with integrating capacitor 108.Therefore, in concrete data output 114, the electric charge on the DELTA electric capacity 126 can be shared zero degree, one or many.Owing to there not being electric charge to shift, not being similar to and setting DAC 116 output voltages and equal voltage on the integrating capacitor 108 so share (sharing zero degree).In any case, for the numerical value of data output 114, the effective charge of sharing is ignored.Therefore, this " feedback loop " of DAC 116, switch 122 and DELTA electric capacity 126 will provide suitable " DELTA " charge value to integrating capacitor 108, to offset the electric charge that imposes on integrating capacitor 108 by measuring electric capacity 102.In addition, because the quantity of the reference charge that applies is dose known amounts (based on DELTA electric capacity 126 and reference voltage 118,120 numerical value), so can easily determine to impose on the total quantity of feedback " DELTA " electric charge that integrating capacitor 108 measures with the relative constant charge that keeps passive network 109 according to digit data stream 114.Namely, digit data stream 114 represents to impose on the quantity of " DELTA " electric charge of integrating capacitor 108 suitably, and next this represent the electric charge that receives from measuring electric capacity 102.By being associated with the voltage that (filtering) initially applies to produce this electric charge from measuring the amount of charge that electric capacity 102 receives, can easily determine to measure electric capacity 102.

[0028] because the figure among Figure 1A is used as typical logical expressions, rather than the side circuit of capacitive transducer implements, the concrete function shown in therefore can be in various alternative embodiments by mutually combination, omit, strengthen or differently implement in addition.For example, comparer and numeral can use the one or more input/output signal pins on the microcontroller etc. to be implemented to simulating changing function 110,116, but and needn't realize with the identification circuit discrete or that separate shown in Figure 1A.Usually need not extra active circuit and can easily realize quantizer 110, this is because many commercially available ASIC or microcontroller products provide cmos digital input, comparer or schmidt trigger function or the similar functions of the signal that is used for receiving at some input pin, perhaps in ASIC or microcontroller, allow the multiplexed of pin or function, for example ADC or DAC, although in certain embodiments, can also use outside multiplexer.In addition, this embodiment generally can implement filtering or other operation to the numerical data 114 that obtains, thereby by using the SIGMA-DELTA technology greatly to simplify the design of capacitive detection circuit.

[0029] the concrete Butut among Figure 1A combines the signal that DAC 116 wherein is squeezed and changes, but integrating capacitor 108 and quantizer 110 do not have inverted notation convention.Although DELTA electric capacity 126 should offer the electric charge of supplying with by measuring electric capacity 102 with " DELTA " on integrating capacitor 108 or opposite impact, can apply in any way this " inversion ".Namely, by adjusting various reference signals 104,112,118,120 symbol or amplitude, and/or by adjusting the configuration of various parts shown in Figure 1A, can make up any amount of replaceable but equivalent embodiment.Several examples of the side circuit that is suitable for Detection capacitance have been described below.

[0030] can operate by any way the essential characteristic shown in Figure 1A.In an operative technique shown in Figure 1B, as by symbol φ ₁, φ ₂Two non-overlapped control signals that indicate trigger the electric charge transfer processing, this processing allows electric charge to be transferred to integrating capacitor 108 from measuring electric capacity 102, and be used for carrying out reverse charging from DELTA electric capacity 126, to adjust the charge level that is kept by integrating capacitor 108.This electric charge shifts with V shown in Figure 1B _X, V _IAnd V _DThe series voltage trace reflect, wherein on its each self-capacitance 102,108 and 126 with reference to V _X, V _IAnd V _DAs shown in FIG., respond low (" 0 ") data value 114, with V _DBe set as the height (" V among Figure 1A _H"), otherwise with V _DBe set as the low (" V among Figure 1A _L").When switch 122 is coupled to integrating capacitor 108, appropriate charge is transferred to integrating capacitor 108 from DELTA electric capacity 126, thereby at voltage V _IThe variation that upper generation is suitable.After initial start period, because negative feedback causes electric charge to be added to integrating capacitor 108 by DELTA electric capacity 126 or subdues from integrating capacitor 108, so voltage V _IWill be usually near comparator voltage V _Cmp

[0031] scope of measurable capacitance is by V _X, V _LAnd V _H, DELTA electric capacity 126 the number of times (N) that is fed of numerical value, each DELTA electric capacity 126 measuring period and can measure the number of times (M) that electric capacity 102 shares with passive network 109 each measuring period and determine.Be electric charge on the passive network 109 and the time between the threshold measuring period.For the first order, can measure the determined value of electric capacity 102 and (suppose that retentive control is to V _CmpVoltage V _I) at C _D(N/M) (V _L-V _Cmp)/(V _X-V _Cmp)) and C _D(N/M) ((V _H-V _Cmp)/(V _x-V _Cmp)) between.As implied above, in many alternative embodiments, can change concrete notation convention and other certain operational parameters for Figure 1A-B.

[0032] existing main reference Fig. 2 (but continuing with reference to the architectural feature shown in the figure 1), the typical technology 200 that is used for execution SIGMA-DELTA electric capacity sample detecting suitably comprises following key step: apply voltage (step 202) to measuring electric capacity 102, allow electric charge to be transferred to the passive network 109 (step 204) that comprises integrating capacitor 108 from measuring electric capacity 102, then based on the electric charge (step 210) on threshold value (step 206) the adjustment passive network.Each that process in each step in 200 is repeated the circulation (step 214) of suitable number, measures to allow accurate SIGMA-DELTA.

[0033] charge step 202 comprises suitably and uses any proper technology that known voltage is imposed on can to measure electric capacity 102.In each embodiment, if suitable, charging voltage (for example, low or high digital output, power supply signal and/or analog) 104 is applied in by excitation controller signal pin or other switch 106.Although should be noted in the discussion above that each switch in the converter 100 is illustrated with concrete arrangement, this only is a kind of example of arrangement.When should also be noted that in each embodiment " use " or " excitation " switch, this " use " or " excitation " can be implemented as and select Closing Switch, select to open the combination in any in switch or other activation switch.Therefore, by the layout according to specific embodiments, utilization is closed or arbitrary combination of opening switch applies voltage.In addition, in one or more pulses (for example, by repeatedly connecting and release-push 106), or by any other technology, charging voltage can impose at least one times can measure electric capacity 102.

[0034] after charging, permission can be measured electric capacity 102 and be shared electric charge with passive network 109, and described passive network 109 just almost can carry out integration and storage to electric charge without amplifier or other active component.In the embodiment that simplifies, passive network 109 only is integrating capacitor 108, and it can be single capacitor; Replacedly, if suitable, passive network 109 can comprise arbitrary number resistance, capacitor and/or other passive element, and the example of a large amount of passive networks is described below.Share electric charge in order to allow to measure electric capacity 102 with passive network, except suspending enough time to allow electric charge to shift outside (for example, not charging to measuring electric capacity simultaneously), without any need for action.In each embodiment, time out can be quite short (for example, if being connected directly to, integrating capacitor 108 can measure electric capacity 102), some time delays may appear (for example perhaps, for electric charge, be arranged on the passive network 109 that to measure the one or more resistance elements between electric capacity 102 and the integrating capacitor 108 and shift by having).In other embodiments, allow electric charge to shift may to comprise effectively to encourage one or more switches (for example, the switch among Fig. 1 106) if or suitable words take other action.In each embodiment, before taking further action, step 202 and/or step 204 can be repeated twice or repeatedly.

[0035] should be noted that, filter capacitor can be coupled to still although can measure electric capacity 102, charge share between the electric capacity can be considered to substantially start from charge step 202 when finishing (for example, voltage is imposed on can measure electric capacity and finish time).In addition, the voltage that the charge share between the electric capacity can be considered to substantially to end on the electric capacity is enough approximate, and can ignore the electric charge of sharing the time.Charge share also can end to apply voltage haply next time, because (for example, the 104 chargings) voltage that applies accounts for leading.Thereby, even being coupled in the passive share system that can measure electric capacity at filter capacitor always, the Low ESR of the voltage source that applies makes can measuring the electric charge that electric capacity shares and can ignore, until the voltage that applies is removed.

[0036] in the time will effectively being transferred to passive network 109 from the electric charge that can measure electric capacity 102, electric charge on the passive network 109 is measured (step 206) suitably, surpass appropriate threshold (step 208) if determine amount of charge, then the electric charge on the passive network 109 changes (step 210).Can implement by any way charge measurement.In various embodiments, the voltage on the passive network 109 represents electric charge from I/O (I/O) pin or the acquisition of other equipment of microcontroller.In many this embodiment, the circuit that is associated with input pin can also analog to numeral (A/D) transformation maybe can be with voltage and the one or more threshold value V that records _THCompare, thus execution in step 206,208 effectively.Concrete threshold value V _TH(for example, reference voltage 112 is by the V that offers quantizer 110 among Fig. 1 _CmpRepresent) can be with embodiment significant change and in time slowly variation.In simple embodiment, the effect (1-position quantizer) of comparer is played in the cmos digital input, and it has the reference voltage of the threshold level that equals the numeral input.Quantizer 110 is connected with passive network and directly maybe can be connected by multiplexer or other switching network.

[0037] have in the situation of hysteresis in input, Schmidt trigger is for example often usefully guaranteed the voltage ratio that records is being set as known state with hysteresis before, thereby is relatively provided similar threshold value to all.Replacedly, can use hysteresis is set as known state, reliably to select between the threshold value that relatively goes up in difference.This can finish by set simply input before the known numeric value of setting hysteretic state is compared.

[0038] when the electric charge on the passive network 109 surpasses appropriate threshold, apply with from (for example measuring relative " DELTA " electric charge of electric charge that electric capacity 102 shares, via the DELTA electric capacity 126 among Fig. 1), change electric charge (step 210) on the passive network 109 to use such as above-mentioned those conventional SIGMA-DELTA technology.In many examples, when electric charge does not surpass threshold value, electric charge on the passive network 109 can also be changed (although being different from the quantity that applies in step 208) (step 211), although this feature is optional in all embodiments.In the situation that a plurality of threshold values can be fed back different charge values.What note is, in the different conditions of recharge cycle step, the electric charge by each electric capacity (for example, can measure electric capacity, DELTA electric capacity, integrating capacitor) shifts and can change direction, shifts but refer to net charge here.By this way, if can measure electric capacity 102 in scope, then the associated voltage that can be held on the passive network 109 of the electric charge on the passive network 109 is approximately equal to threshold value (V _TH) needed electric charge.This is that because control loop, the voltage on the integrating capacitor 108 is approximate during operation to keep constant because the output of quantizer 110 is fed (instantaneous at this with reference to figure 1) via the DELTA electric capacity 126 in the clean degeneration factor.

[0039] in step 206, measure quantized (for example, numeral) numerical value and/or any quantity of obtaining therefrom are (for example, be included in " height " or " low " numerical value in the specific period) can easily be stored in the data that conduct has quantized in the storer, and then suitably by digital filtering or other processing (step 212).In conjunction with the SIGMA-DELTA measuring technique, successfully implement various wave filters, comprise conventional digital finite impulse response (FIR) wave filter, for example triangular filter, average filter and Kaiser wave filter also have infinite impulse response (IIR) wave filter.

[0040] can be individually and/or the concentrated area repeat arbitrarily time to apply voltage, electric charge transfer, charge variation and/or other step (step 214), to realize a plurality of useful features.For example, by obtaining to measure a plurality of quantized values of electric capacity 102, the numerical value that records can easily be extracted in control circuit, filtering, average and/or other digital processing, to fall low noise impact, provides measured value and/or the similar value of cumulative reliability.Many these features are described below.

[0041] many embodiment advantage is, only use passive element in conjunction with the conventional digitial controller such as microcontroller, digital signal processor, microprocessor, programmable logic array, special IC and/or analog, can easily realize general capacitive transducer.A large amount of these products are easily obtained from each commercial sources, comprise Microchip Technologies of Chandler, Arizona; FreescaleSemiconductor of Austin, Texas; With Texas Instruments Inc. (TI) of Dallas, Texas.Many control circuits described here comprise can be used for storing data and instruction number storage (for example, static state, dynamic or flash memory random access memory), described data and instruction are used to carry out each SIGMA-DELTA handling procedure described here.For example, process 200 and can use computer executable instructions easily to be implemented, described computer executable instructions is carried out by one or more control circuit as described herein.

[0042] Fig. 3-8 illustrates several exemplary embodiments of the SIGMA-DELTA capacitive transducer of realizing with integral control circuit with by the simple passive network that capacitor and/or resistance form.Can in many ways any these embodiment be replenished or change, to produce the alternative embodiment of any amount.

[0043] with reference now to Fig. 3 A, typical capacitance sensor 300 suitably comprises controller 302, this controller has at least three input/output signal pins (I/O) 304,306 and 308 and the associated circuits that plays these signal pins of on-off action in controller 102, this switch transition is to VDD-to-VSS (if perhaps suitable, being transformed into other reference value).In the example of Fig. 3 A, I/O ₃(pin 308) with can measure electric capacity 102 and be coupled, and all the other two pin I/O ₁(pin 304) and I/O ₂(pin 306) is coupled with passive network 109, and this passive network 109 comprises integrating capacitor 108, and this integrating capacitor is by measuring electric capacity 102 chargings and discharging by DELTA electric capacity 126, and perhaps vice versa.Integrating capacitor 108 usually is selected to show than the much bigger electric capacity of desired electric capacity that can measure electric capacity 102, and the DELTA electric capacity 126 selected maximum detection amount electric capacity of setting.Moreover concrete capacitance and relation can change according to specific embodiment, and the concrete structure of same signal pin and passive network 109 elements also can change.For example, Fig. 3 B shows " series connection " configuration of three pins, two capacitive transducers 350, and it operates in the mode that is similar to the configuration that " walks abreast " shown in Fig. 3 A.

[0044] in each embodiment, by being controlled at the signal of placing and receiving on I/O (I/O) pin 304,306 and 308, the hardware in the controller 302, software and/or firmware logic suitably sort and control SIGMA-DELTA and measure processing.In exemplary operations, by measuring the voltage on the pin 308, controller 302 is sampled to the electric charge on the integrating capacitor 108 suitably.In other embodiments, can measure voltage on other node.Utilize ADC or schmidt trigger input on control circuit 302 interior available numeral input threshold values, the plate, can quantize in many examples this voltage corresponding to the input of quantizer among Fig. 1 110.In other embodiments, can be provided for voltage on the comparison pin 308 and the analog comparator circuit of suitable reference value 112 (Fig. 1).Although being used for the agreement of data representation can change with different embodiment, greater than the voltage on the integrating capacitor 108 of (pin 308) threshold value can with a logical value (for example, " 1 ") be associated, and can be associated with another logical value (for example, " 0 ") less than the voltage of threshold value.The data of these quantifications are used for aftertreatment by suitably storage (seeing top step 212).Note, if with the input that lags behind, for example the schmidt trigger input is used as quantizer 100, then shown in

state

0,1 method make to lag behind and rest on the signal pin 308 with known state.

[0045] in Fig. 3 C-D, the typical technology for application drawing 3A sensor circuit 300 is shown.In order to control the operation of passive network 109, the charging voltage of substantial constant is (for example, from battery, for example V _DDSupply voltage or other reference voltage) at first impose on the time span that can measure electric capacity 102 substantial constant, in Fig. 3 C-D, be shown as " state 1 ".Signal pin 306 also is driven to same charging voltage, remains on any electric charge on the DELTA electric capacity 126 with removal.Then, by high impedance in the middle of pin 306,308 is placed or " open circuit " state, can isolate and impose on the electric charge that to measure electric capacity 102 can measuring electric capacity 102, as shown in " state 2 ".This intermediateness represents non-overlapped on off state, although there is not clear and definite released state also may realize this technology.Also can insert high impedance status with other and process other conversion.In state 3 by pin 304 is applied logic state voltage, share electric charge from measuring electric capacity 102 to passive network 109 subsequently, the opposite states of above-mentioned logic state and charging voltage is (for example, if be " height " by charging voltage, then apply " low " state, vice versa).

[0046] in the above in the technology, when circuit 300 arrived steady state (SS), the voltage on the integrating capacitor 108 (with reference to pin 304) should keep general constant and approximate greatly the threshold voltage of pin 308 (for example, the be associated V of I/O _TH).Be driven to when low at signal pin 304, the voltage at signal pin 308 places keeps relatively the threshold value near input pin 308 similarly.Thereby when the output of sample quantization device in state 4, quantizer (signal pin 308) is output as the measured value of electric charge on the integrating capacitor 108.Depend on the sampling output (from the input that is associated of signal pin 308) of quantizer, the electric charge that state 5 changes on the integrating capacitor 108.If the sampling of quantizer (signal pin 308) output exceeds threshold value, then state 5A removes electric charge from integrating capacitor 108; Otherwise, do not have (perhaps negligible) electric charge to be removed (state 5B).After being set up (changing the electric charge on the integrating capacitor 108 of passive network 109) at the DELTA electric charge or skipping, signal pin 308 can be placed in high impedance status, with capture electric charge on the passive network 109 be used on pin 308 with post-sampling (state 6).When the data that quantized had been acquired and have stored, these data were can be suitably filtered, extract or other are processed, to determine to measure the numerical value of electric capacity 102.Have in the situation of hysteresis at quantizer (for example signal pin 308), state 1 is set and is input as height, and the low threshold value that lags behind is like this determined output.

[0047] in alternative embodiment, integrating capacitor 108 is by measuring electric capacity 102 discharges and charging by DELTA electric capacity 126, and electric charge is changed when its landing is lower than quantizer threshold.In other modification, the plus or minus electric charge can be shared with integrating capacitor 108 with DELTA electric capacity 126 by measuring electric capacity 102, although there is not electric charge to be shared, also can use other node (for example, the pin 304 among Fig. 3 A) to be used for threshold measurement.

[0048] Fig. 4 A-B shows similar embodiment, and it allows only to realize the SIGMA-DELTA sampling with two signal pins 304 on the controller 302,306.In Fig. 4 A embodiment 400, passive network 109 suitably comprises integrating capacitor 108, and it is connected with isolation resistance 402, this isolation resistance 402 with can measure electric capacity 102 and signal pin 306 is coupled.Fig. 4 A embodiment also comprises and is coupled to signal pin 304,306 DELTA electric capacity 126.Fig. 4 A embodiment (and other) also selectively comprise and the second electric capacity 407 between supply voltage and isolation resistance 402 suppress to increase power supply noise.Select the second electric capacity 407, like this, be coupled to noise on the power supply of node 403 with identical with noise ratio on the power supply of the threshold value that is coupled to quantizer, this quantizer generally is expressed as 110 in Figure 1A.Also can reduce with other layouts the impact of power supply noise, two examples shown in Fig. 9 A-B.Fig. 9 A shows resistance 901 in parallel with electric capacity 407A and that connect with electric capacity 407B, and described electric capacity 407B is coupled to one or more integrating capacitors 108.Fig. 9 B shows two resistance 903,905 that form voltage divider, and it is coupled to one or more integrating capacitors 108, and does not have discrete the second electric capacity.The alternative that comprises the second electric capacity 407A, B or one of utilize in those shown in Fig. 9 A-B for example is particularly useful for the system with a plurality of integrating capacitors 108.Although only show an integrating capacitor 108 together with the second electric capacity 407A, B and alternative, a plurality of integrating capacitors can be shared same node." series connection " modification of 400 shows passive network 109 among Fig. 4 B, and it comprises making can measure the isolation resistance 402 that electric capacity 102 separates with integrating capacitor 108.

[0049] in these two embodiment, use charging pulse to charge to measuring electric capacity 102, described charging pulse is enough short in will basically being blocked by the RC time constant, and described RC time constant produces by integrating capacitor 108 and isolation resistance 402.Equally, charging pulse preferably also is shorter than the RC time constant that can measure electric capacity and isolation resistance.This allow to use identical pin to compress into row and measure measuring electric capacity 102 and charge and integrating capacitor 108 being powered on.In two embodiment, can determine whether share with integrating capacitor 108 from the electric charge of DELTA electric capacity 126 at the voltage that each signal pin 304 or pin 306 record.In the embodiment of Fig. 4 A, signal pin 306 is used to charging voltage imposed on can measure electric capacity 102, and signal pin 304 is used for charging voltage is imposed on DELTA electric capacity 126.The embodiment of Fig. 4 B is different, and signal pin 306 is used for charging voltage is imposed on DELTA electric capacity 126 changing the electric charge on the integrating capacitor 108, and signal pin 304 is used for charging voltage imposed on and can measures electric capacity 102.What note is, in the embodiment of Fig. 4 B, simply be if do not share electric charge from DELTA electric capacity 126, then share electric charge more than 108 time from measuring electric capacity 102 to integrating capacitor, if perhaps do not share electric charge from measuring electric capacity 102, then share electric charge more than 108 time from DELTA electric capacity 126 to integrating capacitor.

[0050] in many these embodiment, " current canceling " voltage can be prior to charging voltage.The timing of control " current canceling " voltage so that in state 0 " parasitism " quantity of electric charge by isolation resistance 402 removals be generally equal to " parasitism " quantity of electric charge that in state 1, is added to integrating capacitor 108 by isolation resistance 402, and with can measure electric capacity 102 before passive network 109 is shared and be in correct charging voltage.This may allow in the passive network 109 than Low ESR, for example be used for the low numerical value of isolation resistance 402, and be used for the on the whole faster time constant of passive network 109, can not measure the requirement of capacitor charging sequential and change.

[0051] can measure electric capacity 102 and share electric charge with integrating capacitor 108 by isolation resistance 402.Because by the RC time delay that resistance produces, this embodiment is than consuming the more multiplex time in sharing electric charge with reference to figure 4 described three-prong embodiment.Yet the number of the switch by reduce to be used for implementing this sensor/logic pin can be with the additional detections channel setting on common chip, thereby allows to improve the efficient among some embodiment.

[0052] typical circuit shown in Fig. 4 A-B can improve with many methods, to realize the other characteristics of any amount.Have among the embodiment of relative accurate timing at controller 302, for example, DELTA electric capacity 126 can be replaced by conventional resistance, and by simply pin 304 (pin 306 among Fig. 4 B) being encouraged the predetermined time section, " DELTA " electric charge can be imposed on integrating capacitor 108.In addition, to be present in any lagging influence in the ADC feature of signal pin 306 in minimizing can be useful to isolation resistance 402.

[0053] a kind of technology for the circuit 400 shown in the application drawing 4A is displayed on the constitutional diagram of Fig. 4 C and the sequential chart of Fig. 4 D.With reference to these figure, by signal pin 306 being placed known (for example logic low) state (state 0), selectively begin the processing that detects measuring electric capacity 102 level.Because isolation resistance 402 produces the RC time constant with integrating capacitor 108, so section blink before at every turn reading circulation, pin 306 (pin 304 among Fig. 4 B) (for example can be placed in known state, logic low state), there is not obviously to affect the quantity of electric charge that is stored on the integrating capacitor 108.Before electric charge was sampled on to integrating capacitor 108, by signal pin 306 is placed known state even very short time, the hysteresis on the pin 306 was known, and controller 302 interior can compensation.If

state

0,1 timing are controlled, then during these states, can also make and flow through the spurious charge that resistance 402 enters integrating capacitor 108 and minimize.

[0054] then, charge to measuring electric capacity 102, and by two pins 304,306 being placed known (height) logic state remove DELTA electric capacity 126, as shown in state 1.By making pin 306 become high impedance status (state 2), can measure trap-charge on the electric capacity subsequently, and then allow subsequently enough time delay, so that electric charge is shared (for example, charge or discharge) to integrating capacitor 108 by isolation resistance 402 from measuring electric capacity 102.From can measuring after electric capacity 102 shared, be applied in or be not applied in (in front in the state 6) from " DELTA " electric charge of DELTA electric capacity 126 based on the voltage that records in integrating capacitor 108 at electric charge.In an illustrated embodiment, be used for to determine that voltage level that whether " DELTA " electric charge be applied in before repeats acquisition from what SIGMA-DELTA processed.In other embodiments, can be only " DELTA electric charge " apply with share before or at other some place of testing process, can measuring voltage (for example, state 3).

[0055] uses the sensor 500 shown in Fig. 5, can realize the further minimizing to the signal pin purposes, wherein can measure electric capacity 102 and be coupled to the individual signals pin 306 of controller 302 by the passive network 109 that integrating capacitor 108 and isolation capacitance 402 form.Be similar to Fig. 4 A embodiment, Fig. 5 A embodiment can also selectively comprise the second electric capacity 407 between supply voltage and isolation resistance 402, and perhaps one of circuit shown in replaceable for example Fig. 9 A-B suppresses to increase power supply noise.In this embodiment, can measure electric capacity 102 reuses potential pulse and charges, described potential pulse has the cycle less than the RC time constant that is produced by isolation resistance 402 and integrating capacitor 108, to reduce or to eliminate being stored in the adverse effect of electric charge on the integrating capacitor 108.Can measure electric capacity 102 by isolation capacitance 402 discharges, as mentioned above, and by placing sparking voltage at pin 306, to continue the known time section by isolation resistance 402 drive currents, " DELTA " electric charge is applied to integrating capacitor 108.Because sensor 500 comprises aforesaid isolation resistance 402, by before sampling, this pin being placed known state, can apply similarly the compensation that lags behind on the pin 306.By the timing of control charging voltage and " electric current elimination " voltage, can also make the parasitic current that during

state

0 and 1, passes through resistance 402 minimum.

[0056] is used for the typical technology of operation sort circuit shown in Fig. 5 B and the 5C.With reference to these figure, selectively set pin 306 so that " electric current elimination " voltage (for example, ground connection) to be provided before charging voltage; Select the length of " electric current elimination " voltage so that removed spurious charge amount mainly equals the spurious charge amount by the charging pulse interpolation.By with after-appliedly have the relatively short duration (with the RC time constant of network relatively) potential pulse, can to measuring electric capacity 102 chargings (state 1), then allow to share electric charge (state 2) by isolation resistance 402 to integrating capacitor 108.After charge share past enough time, by being sampled, the voltage on the pin 306 can measure this electric charge (state 3), and if suitably then " DELTA " electric charge can be applied (or not applying) to integrating capacitor 108 (state 4) based on the voltage of measuring.Moreover, in this embodiment, continue the suitable time by apply suitable voltage at signal pin 306, apply simply " DELTA " electric charge, so that the variation that the charge generation on the integrating capacitor 108 is wanted.

[0057] above-described general structure, concept and technology can change or replenish with many distinct methods, and can use among the embodiment of equivalence again in many differences.For example, two examples of the circuit of electric capacity on the technology for detection hyperchannel shown in above Fig. 6 A-B shows and can use.With reference now to Fig. 6 A,, show typical two channel position sensors 600, it has two detecting electrodes 602,604, and each detecting electrode is corresponding to the electric capacity measured 102 of discussing in the above.When the arbitrary electrode 602 of finger, contact pilotage or other object proximity, 604 the time, the electric capacity of this node is existing related mode to change with object.Another kind of expression method is, by measuring the electric capacity of that electrode channel, can determine with arbitrary electrode 602,604 near to or in contact with the existence of object.

[0058] the employed detection scheme of each passage (A and B) at sensor 600 generally makes parallel about two pin sensors 400 described in Fig. 4 A in the above.Certainly, alternative embodiment may use any other technology of described here or reference.In the exemplary embodiments of Fig. 6 A, then, the pin 306,310 via controller 302 imposes on electrode 602,604 with voltage respectively.Allow each electrode 602,604 to share electric charge by isolation resistance 402A, 402B (difference) with integrating capacitor 108A, 108B.And then, by quantizing the voltage at signal pin 306,310 places, the charge level that remains on each integrating capacitor 108A-B is sampled, by to signal pin 304,308 operation, apply arbitrarily essential " DELTA " electric charge from DELTA electric capacity 126A-B to change the electric charge on the correlation integral electric capacity.

[0059] even further, the symmetry of sense channel makes embodiment can have common elements.For example, required any integrating capacitor, DELTA electric capacity and/or resistance can be shared between a plurality of sensor passages.An exemplary embodiments has been shown in Fig. 6 B.This use of common elements can obviously reduce cost and the size of total system.In fact, can realize various technology, be used for the wide array at alternative embodiment, any discrete component in the signal pin on the shared control unit 302 and/or the passive network 109.

[0060] by implementing many sense channels at common control unit 302, can realize many efficient.Frequently, other electrodes that are used for can measuring the detecting electrode of electric capacity and being used for DELTA electric capacity can easily be formed on standard printed circuit board (PCB), therefore to make copying of these elements on the meaning relatively cheap.Yet, some parts, for example integrating capacitor 108 and isolation resistance 402 can be enough greatly to ensure discrete component.Similarly, in the situation that relate to DELTA electric capacity degree of accuracy, it also can be used as discrete component and implements.In certain embodiments, use printing ink processing etc., can form one or more isolation resistances 402 at PCB, wherein electrically conductive ink has than the high impedance of employed typical material in PCB processes.This can be enough in many examples, because the actual value of isolation resistance 402 does not directly affect degree of accuracy or the performance of this system usually.And in can measuring the relatively little situation of electric capacity 102, then integrating capacitor 108 can also can be made at PCB, such as by using polyimide flexible printed circuit etc.As a result, use conventional manufacturing technology and structure, can easily implement many various features recited above.In addition, by time, frequency, code or other multiplexing technique of any kind, even can further reduce total quantity of desired signal pin and the number of elements in the passive network 109.

[0061] allows to form many dissimilar sensor placements (comprising the multidimensional layout of setting up with one dimension, bidimensional or multidimensional touch pad array) with the conventional arranged in patterns sensing electrode 602,604 of any amount.Replacedly, many " button " type touch sensor can easily be formed by various passages, perhaps can produce other sensor of any amount.

[0062] further, various SIGMA-DELTA detection techniques described herein in conjunction with hyperchannel is integrated easily, provide the efficient application of guard signal.When the detection signal passage, multisensor passage 602,604 connections to common control unit 302 allow to apply guard signal to guard electrode 605.Generally speaking, wish to make each sensor electrode 602,604 and undesired electric signal isolation, comprise from other electrode with from other signals of external sensor 600,650 Spurious receptions.Have common reference and logic voltage because each passage in the sensor 600 can easily be implemented, can easily suppose: the time average of viewed common magnitude of voltage is roughly mutually the same on various sensor electrodes 602,604.By being applied to from the guard signal of low impedance source various electrodes between craticular stage in addition, can reduce so the quantity of false impact.In fact, may to have a sensor electrode of similar detecting electrode voltage swing to all effective for single guard signal.

[0063] the low-impedance voltage source plays a leading role to other coupled signal on the node, just as the low-impedance end comparison high impedance end of voltage divider (perhaps more generally impedance divider) accounts for leading.That is to say, for the set of voltage source, we can be similar to and regard single Thevenin impedance and the single Thevenin voltage of being dominated by the lowest impedance parts as, if this lowest impedance is basically less than the parallel impedance in all other sources.For the purpose of this example, the impedance output of reference voltage, signal pin output, switch or I/O output will have enough low impedance at this Nodes, and other source is unconspicuous at the frequency range place that considers.Similarly, when all the other far-ends of integrating capacitor are driven when having Low ESR (for example, reference voltage etc.), the node that is coupled to the integrating capacitor nearside has sufficiently high electric capacity (and Low ESR), its leading other capacitive couplings source.That is, far-end is driven when having low impedance source, this integrating capacitor can setting voltage and is absorbed most of electric charge from other higher resistance source at near-end.Obviously, the time cycle (or frequency) of considering is also depended in the main impedance in the network.Therefore, on Long time scale (for example sharing), the impedance of connecting with integrating capacitor possibly can't change the state of integrating capacitor as accounting for leading Low ESR parts, and in short time range (for example, charging) on, because series impedance, the impedance of the electric capacity measured on this node may account for leading.By at correct node with correct speed activation switch, can select leading low impedance element, and then suitably guide electric charge.

[0064] although resist technology be selectable and obviously change with embodiment; a technology comprises to guard electrode 605 and applies protection voltage; described protection voltage approximates greatly the voltage that imposes on active electrode (for example, electrode 602 or 604) between charge period.At electric charge from the active sensor electrode to relevant integrating capacitor (for example; be used for electric capacity 108A or the 108B of sensor 600 and be used for the electric capacity 108 of sensor 650) shift finish before (step 204 of Fig. 2); the voltage that imposes on guard electrode 605 changes, and approximates greatly the voltage (active sensor electrode and correlation integral electric capacity are common near same voltage when charge share occurs) on active sensor electrode and the correlation integral electric capacity.Because the threshold voltage of quantizer is approximately equal to the voltage on the correlation integral electric capacity when feedback loop is controlled; (for example can use the dependent quantization device; signal pin on the identity element, I/O) threshold voltage control protection voltage, as for example agency of voltage on the correlation integral electric capacity in the system shown in Fig. 6 B.Replacedly, when impedance divider output susceptibility is similar to the quantizer threshold susceptibility and becomes ratio with power supply, can use impedance divider reduction power changing sensitive degree; The example of this impedance divider illustrates by the voltage divider that is formed by resistance 606,608 among Fig. 6 A.In another embodiment, protection swings (with the electric charge that shifts from guard electrode) and may be repeated to from of charge transfer process another and repeat to change (charge transfer process comprise apply step, allow step and change step).This protection voltage swing may be on average to the voltage swing identical with voltage swing on detecting electrode.Swing and have steady state value in the situation in addition if the variation that protection swings has zero in some cases, this so that the pulse code modulation (PCM) resist technology without any need for extra parts.Skew between guard electrode voltage and the detecting electrode voltage can not affect the serviceability of this protection, because for the electric charge by electric capacity shifted, important only was change in voltage.

[0065] utilize the impedance divider that uses two

resistance

606 and 608 although should be noted in the discussion above that sensor 600, this only is an exemplary types of operable impedance divider.Particularly, common impedance divider comprises two passive impedances of series connection, and each passive impedance is coupled at least two nodes.One of these nodes are two common nodes that impedance is coupled.This common node provides the output of this impedance divider.This impedance divider is output as voltage and/or the electric current function in time that imposes on " not common points ".The simple case of impedance divider is voltage divider, and it comprises two electric capacity or two resistance (for example resistance 606,608).Yet, can also use more complicated impedance divider.These more complicated impedance dividers can comprise unmatched electric capacity, resistance or the inductance of serial or parallel connection.In addition, single impedance can have the combination of capacitive character, resistive or inductive feature.

[0066] if suitable, can use the feature relevant with signal pin 604 (Fig. 6 A) or 310 (Fig. 6 B) to apply protection voltage.In the embodiment of Fig. 6 A, for example, use

resistance

606 and 608 to consist of power supply (V _DD) voltage divider, in the voltage divider circuit or outside with pin 602 effectively transition resistance 608 produce two separation voltages that impose on guard electrode 605.Embodiment shown in Fig. 6 B shows the allotter circuit that comprises resistance 608 and capacitor 614 similarly, and signal pin 310 control imposes on guard electrode 605 with charging voltage or is discharged into the protection voltage (playing more the effect of circuit 500 shown in Fig. 5 A when it shares electric charge) of threshold voltage.For most effectively protection, the impedance that drives protection voltage should be less than the total sensors coupled impedance to guard electrode.Can also use various other resist technologies, it comprises active analog element, for example the impact damper exclusive disjunction amplifier (OP-AMPS) of tracking transducer or reference channel.Although Fig. 6 A-B usually based in conjunction with the described embodiment of top Fig. 4 A-D, can be applied in the protection concept on the capacitive sensor of wide array.Yet, protect as not being based upon the optional feature on all embodiment.

[0067] many replacement detection schemes have used on discrete elements and/or the controller 102 logic pin sharing on a plurality of sense channels.For example, the sensor 650 shown in Fig. 6 B shows simple technique, thereby DELTA electric capacity 126 and integrating capacitor 108 share between two detecting electrodes 602,604.Sensor 700 shown in Fig. 7 A shows simple technique similarly, uses this simple technique, and the signal pin 308 of using DELTA electric capacity 126 can share between two sense channels (electric capacity 102A-B is represented by measuring).In this embodiment, sensor 700 operates in the mode that is similar in the above in conjunction with the described sensor 350 of Fig. 3 B, but charge feedback is to the DELTA electric capacity 126A-B side that provides by common signal pin 308.Whether usually, this embodiment changes phase place, responsive to the transformation on the corresponding DELTA electric capacity (126A and 126B) to determine concrete integrating capacitor (for example 108A or 108B).Particularly, according to which side that drives integrating capacitor with Low ESR, each integrating capacitor can selectively be shared electric charge or intercept from the electric charge transfer that can measure electric capacity or DELTA electric capacity.Therefore, can allow each DELTA electric capacity in the situation that do not affect and to measure electric capacity and change, and then signal pin 308 can share with a plurality of sensors, reduce number of pins.For changing capacitor system, driven detecting electrode (for example 802 among Fig. 8 A) can also share with a plurality of sensors.These concepts can be applied to the other sense channel of any amount similarly, measure re-using between the electric capacity 102 with further element and/or the signal pin of improving a plurality of.

[0068] Fig. 7 B comprises the constitutional diagram 750 of the typicalness sequence that sensor 700 is shown.Together with reference to figure 7A, 7B, the first state 1 is to make and can measure capacitor discharge by pin 304 and 312 being set to 0, uses simultaneously the voltage with pin 306,310 relevant I/O measurement (quantification) integrating capacitor places.At the example shown in the transformation that is used for pin 304,306 constitutional diagram, the voltage that described transformation indication is measured at pin 306 places during state 1 be high (quantized data 1), and the voltage that is used for transformation indication pin 310 measurements during state 1 of pin 310,312 constitutional diagram is low (quantized data 0).According to they measured values separately, these different conditions change the different DELTA electric charges that cause among the state 5-8 to be shifted.It is also noted that, the transformation of from high to low impedance may occur in state according to pin 304 and 312 fronts in the measurement of front and the state 8 in state 1.Because this transformation, any voltage swing at pin 306 and 310 places will cause from stray capacitance and DELTA electric capacity 126A-B to they some charge shares of integrating capacitor 108A-B separately.This may cause in the skew of determining to measure in the electric capacity, but as long as it is little and constant, it just can be deducted, and then will be minimum on the impact of dynamic range.

High impedance status in the middle of [0069] second state 2 comprises.In this state, signal pin 304,306,310 and 312 is all temporarily remained on high impedance status, and it is low that pin 308 drives DELTA electric capacity 126A-B.This causes intermediateness, makes each capacitor uncoupling with temporary transient trap-charge in these capacitors.This guarantees not exist superposed signal, and it may not inadvertently arrange undesired electric charge at capacitor in addition.

[0070] third state 3 makes the integrating capacitor 108A that is coupled to DELTA electric capacity 126A-B, the electrode of 108B be in logic high voltage.This causes that the voltage that can measure on the electric capacity 102A-B changes, and shares electric charge with their integrating capacitor 108A-B separately.Simultaneously, be Low ESR by signal pin 306,308 is driven, the electric charge transfer that is coupled by DELTA electric capacity 126A-B gets clogged.

[0071] because the both sides of these capacitors all are set to the identity logic high voltage by pin 306,308 and 310, the electric charge that the 4th state 4 is removed on DELTA electric capacity 126A and the 126B.

[0072] the 5th state 5 makes pin 306 be in high impedance status, and this remains on the integrating capacitor 108A electric charge.Before it changed in subsequent state 5, concerning can measuring electric capacity 102A, this was the middle high impedance status on the signal pin 304, and stoped electric charge not inadvertently to be arranged on the integrating capacitor 108A.What note is, only is coupled to the I/O of integrating capacitor 108A by uncoupling, and described I/O has the voltage of quantized data measured value 1 at pin 306 places.The pin 310 that is coupled to integrating capacitor 108B keeps being driven to logic high voltage, and described integrating capacitor 108B has the voltage of quantized data measured value 0 at pin 310 places, and this is because integrating capacitor does not require the electric charge change by DELTA electric capacity 126B.

[0073] the 6th state 6 drives signal pin 304 to low logic level, so that the DELTA electric charge can pass to integrating capacitor 108A by DELTA electric capacity 126A in later step 7.What note is that pin 310 keeps being urged to logic high, is blocked in and shifts this DELTA capacitance charge between 126B and the 108B.What also note is that the low logic level transformation on this pin 304 also causes electric charge in this step rather than shares with DELTA electric capacity from stray capacitance in the next step 1 as has been described.

The voltage that [0074] the 7th state 7 changes on the pin 308, to remove electric charge by DELTA electric capacity 126A from integrating capacitor 108A, the electric charge on the integrating capacitor 108B is basically unaffected simultaneously.

[0075] final state 8 comprise for integrating capacitor (for example, 108B) second in the middle of high impedance status, it does not need the electric charge in the step 7 to change, and prepares their and be used for sharing of later step.This is each capacitor of uncoupling again, with trap-charge in these capacitors temporarily.

[0076] after final state 8 was finished, the method turned back to step 1, and state 1-8 is carried out again.Should be noted in the discussion above that this order according to the measured value of the voltage on pin 306, the 308 integrating capacitor 108A-B of place and be suitable for determining that the quantized data (for example, 0 or 1) that they can measure electric capacity 102A separately bears results.Be used for measuring electric capacity 102A and pin 304,306 and can measure electric capacity 102B and pin 310,312 step order only is the voltage on the pin 306,310 specifically to be measured the example of (and quantification) at exemplary step 1, according to the measurement in this duplicate measurements cycle, arbitrary sequence of states can appear can measuring on electric capacity and the integrating capacitor.Usually, in the measurement that can measure electric capacity, two states order will appear on the relevant pins, and two types the quantized data that obtains (for example 0 or 1) will become the part for any result who determines to measure electric capacity.

[0077] should be noted in the discussion above that this embodiment has several advantages.For example, because public pole (that is, pin 308) is always driven, therefore can reduce significantly the impact of stray capacitance.Secondly, sensor 700 can reduce and uses the IO state and to the sample quantity of the circulation that spends of a plurality of electric capacity, this is because its allows parallel sampling (that is, quantizing simultaneously) on a plurality of I/O.At last, many when measuring electric capacity when detecting, it allows the IO of obvious much less.This embodiment can also reduce the sensitivity to external noise during the integrating capacitor charge measurement, described external noise is by measuring electric capacity or other relevant stray capacitance coupling, described electric capacity or the stray capacitance measured can be measured electric capacity (that is, pin 304,312) node ground connection and be coupled to pin 304,312 by being coupled to.

[0078] although the embodiment shown in top generally emphasizes what is called " absolute capacitance " sensor, wherein can measure electric capacity about the local system earthmeter, similar concept can be applicable to the capacitive transducer of other type.For example, Fig. 8 A shows another embodiment of sensor 800, and it is designed to work with so-called " driven electric capacity " or " conversion electric capacity " sensor.When integrating capacitor 108 and DELTA electric capacity 126 with can measure electric capacity 102 and connect the time, sensor 800 is " series connection " sensor.In the embodiment shown in Fig. 8 A, can measure electric capacity 102 and be formed by two separate mesh electrodes 802,804, the signal pin 304,306 of use controller 302 can be with each electrode drive to one voltage.When drive waveforms on " driving " electrode 802, use the capacitive couplings of SIGMA-DELTA detection technique recited above between can detecting electrode 802,804, the electric charge that detects between electrode 802,804 and shift to the passive network 109 that comprises integrating capacitor 108.The result is that in the situation that obviously do not change, the sensor that depends on capacitively coupled change between " driving " and " detection " electrode can easily be realized above-mentioned concept.Note foregoingly, conversion can be measured other conductor and/or the dielectric impact that electric capacity can be subject to any amount, so that produce complicated total effective capacitance near electrode 802,804 parts.In addition, be similar to described for DELTA electric capacity and shown in the constitutional diagram 750, the phase deviation of during the repetition of charging cycle, sharing step can also be implemented block or allow with change capacitive transducer in " driving " electrode share electric charge.

[0079] Fig. 8 B comprises constitutional diagram 825, and it illustrates the typicalness order for sensor 800.Together with reference to figure 8A and 8B, in the first state 1, the state of the I/O4 by changing signal pin 310 by DELTA electric capacity 126 (Cd), can add the DELTA electric charge to integrating capacitor 108.In state 1, on 310 logic state from this change that is low to moderate high logic level (or just resting on lower) as F (V _CI) function, depend on that the front of the voltage on pin 308 place's integrating capacitors 108 in the state 7 in front quantizes.As an example, function F (V _CI), if the voltage ratio at integrating capacitor 108 places is for the threshold voltage V of the I/O3 of signal pin 308 in circulating in front _THHigh (that is, electric charge is low on the integrating capacitor, and then voltage drop is less than expection), then pin 310 remains low.Otherwise, if the voltage ratio threshold voltage at integrating capacitor 108 places low (that is, electric charge is high on the integrating capacitor, and then voltage drop is greater than expection), then pin 310 is driven to height, to raise at 308 voltage by removing electric charges from integrating capacitor 108 by DELTA electric capacity 126.In at every turn the repeating of electric charge transfer processing, when I/O1 from lowly change height into, when adding electric charge to integrating capacitor, electric charge is also by the capacitor C measured between electrode 802 and 804 _X102 shift.Under the control of SIGMA-DELTA system, add electric charge and remove electric charge by DELTA electric capacity 126 by measuring electric capacity 102, the electric charge on the integrating capacitor 108 keeps constant by negative feedback control is general.

[0080] thereby, the front voltage measurement based at the I/O3 place of pin 308 upper integral electric capacity utilizes DELTA electric capacity 126, state 1 is removed (being 1a) or is not removed (being 1b) electric charge from integrating capacitor 108.In alternative embodiment, this measurement may be implemented with the whole bag of tricks, and the voltage of for example measuring on the integrating capacitor can use pin 306.

[0081] state 2 is the middle high impedance status on the both sides (that is, signal pin 306,308) of integrating capacitor 108.This is the caputure integral electric charge on integrating capacitor 108, so that do not change thereon electric charge for any timing error in the output of signal pin.Pin 304 keeps driving as low, and pin 310 is retained in the state of its front.

[0082] in state 3, signal pin 308 is set to low logic state (for example, ground connection).What note is to measure in front the voltage on the pin 308 in the state 7, and should approach the input threshold value relevant with I/O3 with signal pin 308.By driving 308 to logic low state and changing voltage on integrating capacitor 108 1 sides, the voltage at detecting electrode 804 places also changes, and integrating capacitor 108 with can measure electric capacity 102 and any other stray capacitance is shared electric charge, described stray capacitance is coupled to the electrode at signal pin 306 and sensor 804 places.In this typical case, and can measure electric charge that electric capacity 102 shares and be in equidirectional by the I/O1 that drives on the pin 304 for the high electric charge that shifts in the step below, although this needs not to be the situation in all embodiments.Although the meaning of this example is the function as the conversion capacitive transducer, but, because the change of arbitrary voltage on 804, share electric charge on the integrating capacitor 108 just as other " absolute capacitance " sensors, occuring that this paper other places are described from stray capacitance.This stray capacitance is shared on integrating capacitor 108, and in this example, will add electric charge to it, and minimizing pin 308 is in the measuring voltage on the integrating capacitor 108.

[0083] in the 4th state 4, when I/O1 on the pin 304 changed into logic high voltage from logic low, 108 shared electric charge from electrode 804 to integrating capacitor, and then removed any electric charge on the DELTA electric capacity 126.Especially, in this state, pin 304 is driven to height, and pin 310 is low.This allows electric charge by measuring electric capacity 102 (C _X) share to integrating capacitor 108 from electrode 804.Simultaneously, at signal pin 310,308 places, the voltage on the both sides of DELTA electric capacity 126 is driven to low.Because the node at pin 308 places is in Low ESR, therefore in this step, there is not electric charge to transfer on the integrating capacitor 108 by DELTA electric capacity 126.

[0084] the 5th state 5 is another high impedance status of uncoupling integrating capacitor 108 both sides.

[0085] the 6th state 6 drives can measure electric capacity (C _X) 102 detecting electrode 804 is logic high voltage, blocking the charge share by detecting electrode 804 couplings, and permission is shared with DELTA electric capacity 126.In next measuring process, drive Low ESR at the signal pin 306 of I/O2, make integrating capacitor 108 shieldings be coupled to any noise of this electrode.It also allows electric charge by integrating capacitor 108 and the nodes sharing that is connected to signal pin 308 and DELTA electric capacity 126.Yet, by driving logic high voltage at electrode 804, also change the voltage at signal pin node 308 places.This any stray capacitance and integrating capacitor 108 that causes that again electric charge passes through on the pin 308 is shared.Although this needs not to be the situation among other embodiment,, in this example, be Low ESR because signal pin 310 is driven, electric charge is also shared with DELTA electric capacity 126.What note is, with can to measure sharing of electric capacity in the state 3 different, be driven to different voltages in the state 1 when changing the electric charge on the integrating capacitor at signal pin 310, this spurious charge will be in the reverse direction of the electric charge that shifts by DELTA electric capacity 126.Change electric charges more proportional with size to the voltage of stray capacitance and DELTA electric capacity and will share and be tending towards increasing voltage on the integrating capacitor 108, and be reduced in the voltage of pin 308 places measurement.If pin 310 is in the anti-state of high impedance, this can be significantly reduced (reducing to only stray capacitance).Because it be high driving 306, if the voltage transfer on 308 less than be used for deducting step 4 electric charge 310 on voltage transfer, so, in conversion capacitive character SIGMA-DELTA processing, still can from net charge, deduct DELTA electric capacity 126.

The voltage that [0086] the 7th state 7 is measured on the integrating capacitor 108.When pin 308 was in high impedance status, with respect to the voltage that drives at detecting electrode by signal pin 306, (because integral charge) can measure at pin 308 places the voltage on the integrating capacitor 108.This measurement can comprise the voltage at integrating capacitor 108 places and threshold voltage V _THCompare, so that the result of quantification to be provided.Then, during state 1-3, (that is, whether it is than threshold voltage V with voltage measurements on the integrating capacitor 108 _THHigh) for the F (V that repeats that circulates next time _CI) in, determine how the electric charge on the integrating capacitor may be changed by DELTA electric capacity 126.

[0087] therefore, SIGMA-DELTA closed-loop control to electric charge on the integrating capacitor 108 will be caused to repeating of state 1-7, and the conversion electric capacity between

potential electrode

802 and 804 can be come with the filtering measured value of quantized result.The conversion electric capacity of this measurement can be further used for inspected object approaching or any other purpose with respect to sensor.

What [0088] note is, because stray capacitance, voltage at step 3 sharer node place of the integrating capacitor 108 relative with driven node in 6 changes and causes that undesired electric charge shifts, and can cause by measuring the charge share of electric capacity 102 or DELTA electric capacity 126 in the direction opposite with anticipated orientation." absolute capacitance " behavior of this representation conversion capacitive sensor.These voltages change less with respect to driving DELTA electric capacity 126 employed voltage swings by signal pin 304 drive electrodes 802 and signal pin 310, stray capacitance will have less impact, and the function of conversion capacitive character SIGMA-DELTA measuring system is unreasonable thinks.

[0089] turns to now Fig. 8 C and 8D, show the second embodiment of conversion capacitive sensor 850.Conversion capacitive sensor 850 be line sensor also, namely measuring in being connected of electric capacity 102 and integrating capacitor 108, can measure electric capacity 102 in parallel with DELTA electric capacity 126.Also have, in this embodiment, near threshold voltage V _THVoltage V _GProduced by the voltage divider that comprises resistance 812 and 814.Embodiment is the same with the front, can measure electric capacity 102 and be formed by two

separate mesh electrodes

802 and 804, and each separate mesh electrode can utilize the signal pin 304,306 of controller 302 to be urged to a voltage.When drive waveforms on electrode 802, capacitive couplings between the electrode 802 and 804 (by measuring electric capacity 102 indication) can utilize the SIGMA-DELTA detection technique to detect, with the electric charge that detects between electrode 802,804 and shift to the passive network 109 that comprises integrating capacitor 108.

[0090] Fig. 8 D comprises the constitutional diagram 875 of the typicalness order that shows sensor 850.With reference to figure 8C and 8D, the first state 1 comprises middle high impedance status together.In this state, signal pin 306,308A and 308B all are maintained at high impedance status, and pin 304 drives and is logic low-voltage, and pin 310 drivings are logic high voltage.This causes making the intermediateness of each capacitor uncoupling, with temporary transient trap-charge in these capacitors.This guarantees not exist superposed signal, and it may not inadvertently arrange unwanted electric charge at capacitor in addition.

[0091] in the second state 2, the voltage V that the voltage on node 851 place's integrating capacitors 108 is set to generate _G, described V _GBe implemented and be substantially equal to measure I/O (for example, IO3) threshold voltage V _THParticularly, pin 308A provides logic high voltage (for example, V _DD), pin 308B provides logic low-voltage, and (for example, GND), and resistance 812 and 814 provides voltage divider, and this voltage divider produces voltage V at node 851 places _GIn an exemplary embodiments, resistance 812 and 814 equates basically, therefore, inputs threshold with CMOS, and the voltage that produces is similar to 1/2V _DDExist many methods to be used for using passive element and switch (for example, I/O or DAC) to apply the voltage that produces, and this only is an example.The threshold voltage of numeral input is the voltage that low and high input is distinguished.Certainly, this only is an example, and in other embodiments, hope can utilize other numerical value.For example, utilize in the situation of Schmidt trigger input V at I/O _Dd/ 3 voltage may be similar to the input threshold value of I/O3, and it is high that described input threshold value only is set as logic.Should also be noted that and do not use in certain embodiments voltage divider.Replace it, in certain embodiments, controller 302 comprises that inherently generation is near V _THSuitable voltage V _GAbility.

[0092] should also be noted that to have near threshold voltage V _THThe driving node 851 of the voltage Vg that produces in step 2-3, reduce voltage swing on the electrode 804, reason is the electric charge on the SIGMA-DELTA feedback loop control integrating capacitor 108, when signal pin 306 drives node 804 (in

step

5,6,7), keeping voltage on the node 851 near threshold voltage, and can measure the input that is connected to node 851 (for example 308A).Owing to having minimized the electric charge that does not move through stray capacitance, be that fixed voltage (for example, GND) does not have much relations so keep to a

great extent

804 and 851 place's voltage constants to make stray capacitance.What note is, if be to implement with the I/O2 on the pin 306 to the measurement of the voltage on the integrating capacitor 108, then node 306 may use similar formation voltage Vg to drive impact with minimum parasitic capacitance.

[0093] in the third state 3, according to the front the 308A place to integrating capacitor 108 on the measurement of voltage, the DELTA electric charge is transferred to integrating capacitor 108 and/or electric charge is shared between electrode 804 and integrating capacitor 108.Particularly, drive pin 310 be the front at the 308A place function F (V to the voltage of integrating capacitor 108 measurements _CI).As an example, choice function F (V _CI), if so that the voltage of integrating capacitor 108 (for example at node 851 places) is higher than the threshold voltage V of front I/O3 in the repetition of measuring circulation _TH(that is, the electric charge on the integrating capacitor is low, and voltage drop is less than what wish), then pin 310 remains on logic high voltage.Otherwise, if the voltage at integrating capacitor 108 places is lower than threshold voltage (that is, the electric charge of integrating capacitor is high, and voltage drop is larger than what wish), then drive pin 310 to logic low-voltage, to remove electric charge by DELTA electric capacity 126 from integrating capacitor 108.In all situations, when I/O1 from logic low-voltage change logic high voltage into, when adding electric charge to integrating capacitor, electric charge is also by the capacitor C measured between electrode 802 and 804 _X102 shift.Under the control of SIGMA-DELTA system, add electric charge and remove electric charge by DELTA electric capacity by measuring electric capacity, the electric charge on the integrating capacitor is probably kept constant by negative feedback control.

[0094] thereby, based on the front at the I/O3 place to the voltage measurement on the pin 308A of integrating capacitor, state 3 is shared electric charge between electrode 804 and integrating capacitor 108, perhaps utilize DELTA electric capacity 126 to remove electric charges from integrating capacitor 108.

[0095] the 4th state 4 comprises another middle high impedance status, and it guarantees not have may not inadvertently not want capacitor setting in addition the signal of electric charge.The 5th state 5 by the I/O2 on the signal pin 306, is set to logic high voltage with receiving electrode 804 again.The 6th state 6 arranges can measure electric capacity (C _X) 102 and DELTA electric capacity (C _D) electric charge on 126, the transformation in repeating with next that prepare charge transfer process.Particularly, arrange logic high voltage at pin 310, and arrange that at pin 306 logic high voltage makes 126 discharges of DELTA electric capacity.Simultaneously, arrange logic low-voltage by signal pin 304 at electrode 802, the electric capacity measured that is coupled to electrode 804 is recharged.By on the electrode 804 in can measuring electric capacity 102 and in a side of the integrating capacitor 108 that is coupled to DELTA electric capacity 126 low-impedance voltage being set, electric charge can maybe can not measured electric capacity 102 by DELTA electric capacity 126 and shift to integrating capacitor 108 during this step.This numerical value of guaranteeing integrating capacitor 108 keeps accurate transfer charge to represent during the step in front, and just can measure it in the situation of the noise that is not subject to detecting electrode 804.

[0096] the 7th state 7 is measured the voltage at integrating capacitor 108 places.When pin 308 was in high impedance status, (because accumulation electric charge) can measure voltage on the integrating capacitor 108 voltage of node 851 places (for example) at pin 308A or pin 308B.This measurement can comprise voltage and the threshold voltage V at integrating capacitor 108 places _THComparison, so that quantized result to be provided.Then, during state 3-5, the measurement result of voltage on the integrating capacitor 108 is used for the F (V of next circulation _CI) in (that is, whether it is higher than threshold voltage V _TH), determine how the electric charge on the integrating capacitor can change by DELTA electric capacity 126.

[0097] therefore, will cause SIGMA-DELTA closed-loop control to electric charge on the integrating capacitor 108 to repeating of state 1-7, and the filtering measurement of quantized result be can be used for conversion electric capacity between potential electrode 802 and 804.The conversion electric capacity of this measurement can be further used for inspected object approaching with respect to sensor.

[0098] as mentioned above, sensor examples measure conversion electric capacity rather than absolute or ground connection reference capacitance shown in Figure 8.These embodiment reduce background or stray capacitance to the negative effect of the electric capacity measured, thereby the application of the parasitic trace electric capacity that has higher proportion is particularly useful, and for example fingerprint line (fingerprintridge) detects and the capacitive touch detection.

[0099] for example, when driving the voltage V that produces at node 851 _gWhen probably equaling to be coupled the input threshold voltage of signal pin of 851 (for example, wherein they are the 308A/B of I/O), the voltage swing quantity on institute's detecting electrode 804 can be remained relatively low level by the SIGMA-DELTA FEEDBACK CONTROL.This can reduce the sensitivity to stray capacitance fully.Namely, owing to relatively keeping near threshold voltage at the voltage on node 851 place's integrating capacitors 108 during the steady state operation, when driving voltage on node 851 (with 306 floating), and on 306, during driving voltage, do not drive node 851 by signal pin 308A/B.Similarly, because signal pin 306 is driven to the result's (rather than driving signal pin 306 to some other voltage) who is similar to when node 851 place's voltages being urged to one of 308A/B locating to input threshold voltage, the voltage swing on the maintenance electrode 804 is for relatively low.Determine voltage difference between 851 and 306 by passing voltage (and electric charge) on the integrating capacitor, the voltage on the described integrating capacitor (and electric charge) is by the control of SIGMA-DELTA feedback loop.Can apply by any way 306 and node 851 on these voltages.In various embodiments, apply approximate threshold voltage by the logic of utilizing pin 308A-B, with the part of excitation or de-energisation divider network, thereby produce suitable voltage.Replacedly, can apply approximate voltage by digital to analog converter or by any other technology.

[00100] even, to shown various circuit and technology can be implemented more improvement and change here.Can use the above-mentioned technology that has or do not have extra active analog element, implement higher-order SIGMA-DELTA modulator.

[00101] in addition, for example, can reduce various noise sources by using the noise dither technology.Particularly, known conventional single order SIGMA-DELTA converter especially is vulnerable to the impact of noise " tone " (that is, repetitive noise form).These tones can produce for the noise of certain constant input output (like this, having " dead band " in the situation of capacitive character sensitivity low (or replacedly, high level error)), cause the slightly reduction of microvariations response of initial conditions.More complicated by utilizing (that is, more high-order) SIGMA-DELTA technology perhaps replacedly by the low power noise of smallest number is injected the SIGMA-DELTA converter, can be avoided tone.A kind of technology of be used for injecting noise comprises noise dither is applied to ADC reference voltage (for example, the voltage among Fig. 1 112).Can in any number of software or other logic, generate this shake, and this shake is applied to each sense channel simultaneously to improve response.

[00102] as mentioned above, be used for determining that equipment and the method for electric capacity specifically can be applicable to approaching sensor equipment.Now turn to Figure 10, block diagram shows the exemplary electronic system 10 that is coupled to approaching sensor equipment 11.Electronic system 10 is used for personal computer, portable computer, workstation, personal digital assistant, video game machine, communication facilities (comprising wireless telephone and information transfer apparatus), the media device of expression any type, and this media device comprises that logging machine and player (comprising TV, cable box, music player and video player) maybe can accept to input or the miscellaneous equipment of process information from the user.Therefore, each embodiment of system 10 can comprise processor, storer or the display of any type.In addition, the element of system 10 can be via bus, network or other wired or wireless interconnected communicating.By comprising any type of interface or the connection of I2C, SPI, PS/2, USB (universal serial bus) (USB), bluetooth, RF, IRDA, or the arbitrarily wired or wireless connection of other type, approaching sensor equipment 11 can be connected to system 10, has enumerated several non-limitative examples at this.

[00103] approaching sensor equipment 11 comprises controller 19 and surveyed area 18.11 pairs of approaching sensor equipment are inputted the position sensing of 14 (they can be provided by one or more fingers, contact pilotage and/or other input object) in surveyed area 18, and can be by measuring because the input 14 electric capacity results change that cause detect input 14." surveyed area " 18 as used herein be included in widely approaching sensor equipment 11 top, on every side, the inside and/or near any space of approaching sensor equipment 11, the position that wherein sensor can inspected object.In conventional embodiment, surveyed area 18 launches a distance from sensor surface and enters the space one or more directions, until signal to noise ratio (S/N ratio) has stoped input to detect.This distance can be on less than millimeter, several millimeter, several centimetres or more quantity rank, and can change significantly with desired sensor electrode size, sensor design and/or sensor performance (for example, degree of accuracy or resolution).Therefore, the flatness in particular detection zone 18 or curvature, size, shape and exact position will change significantly with the different of embodiment.

[00104] in operation, by measuring the measured electric capacity relevant with a plurality of detecting electrodes, approaching sensor equipment 11 suitably detects inputs 14 position, the impact of its examined regional 18 interior one or more fingers, contact pilotage and/or other object.And, using controller 19, approaching sensor equipment 11 offers electronic system 10 with indication electricity or electronics of position.As discussed previously, this system 10 suitably processes this and indicates to accept from user's input being used for any suitable purpose, and the response that produces any appropriate.

[00105] approaching sensor equipment 11 can use any other of discritized array or capacitive sensor electrode to arrange to support the surveyed area 18 of any amount.Approaching sensor equipment also can change the information type that provides, (for example for example be provided as " one dimension " positional information of scalar, along surveyed area), as " two dimension " positional information of combinations of values (for example, cross over two dimension horizontal/vertical, angle/radially or any other axle), as " two dimension " image that approaches of array of values etc.

[00106] utilize above-described various technology, the controller 19 that sometimes is called as approaching sensor processor or touch sensor controller is indicated the processing that is used for measuring electric capacity usually.Here, controller 19 is also communicated by letter with electronic system 10.Controller 19 can be carried out various other processing, to realize approaching sensor equipment 11.For example, the single electric capacity of measuring can be selected or connect to controller 19, based on numerical evaluation position or the movable information that can measure electric capacity, position or the motion of report when reach threshold value, and effectively clap/strike/carves/fastening/make a sign with the hand sequentially or any a plurality of different processing it being reported to electronic system 10 or its indication explained before to the user with waiting for.

[00107] in this instructions, term " controller " is defined and comprises the one or more processing element that are suitable for carrying out described operation.Thereby controller 19 can comprise all or part of one or more integrated circuit, firmware code and/or software code.

[00108] moreover, the term that uses in using such as this, term " electronic system " refers to the equipment of any type widely, it is communicated by letter with approaching sensor equipment 11.Therefore, electronic system 10 can comprise equipment or a plurality of equipment of any type, wherein can realize or coupled with touch sensors equipment.Use any suitable technique, this approaching sensor equipment 11 can be embodied as the part of electronic system 10 or be coupled to electronic system 10.Therefore, as non-limitative example, electronic system 10 can comprise any type computing equipment, media player, communication facilities or another input equipment (for example, other touch sensor equipment or keyboard).In some cases, electronic system 10 itself is the peripherals of larger system.For example, electronic system 10 can be that data input or output equipment, for example remote control or display device (for example, remote-controlled television set), and it utilizes suitable wired or wireless technology and computing machine or media system to communicate.Should also be noted that all parts (processor, storer etc.) in the electronic system 10 can implement as the part in the whole system, as the part in the touch sensor equipment or as its combination.In addition, electronic system 10 can be master or the slave of approaching sensor equipment 11.

[00109] should also be noted that term " approaching sensor equipment " not only comprises conventional approaching sensor equipment, but also comprise a large amount of equal equipment of the position that can detect one or more fingers, contact pilotage and/or other object.This equipment can include, without being limited to touch-screen, touch dish, touch pad, biometrics evaluation apparatus, calligraphy or Character Font Recognition equipment.Similarly, term as used herein " position " or " object space " comprise absolute and relative positional information widely, also comprise the spatial-domain information of other type, and for example speed, acceleration etc. are included in the motion measurement in one or more directions.Various forms of positional informations also can comprise the time history part, as in the situation of gesture identification etc.Therefore, approaching sensor equipment can suitable detection exists or lacks more information than object, and can comprise a large amount of equivalents.

[00110] it is also understood that mechanism of the present invention can distribute as various forms of program products.For example, the approaching sensor program that the readable computer signal supports media (signal bearing media) can be implemented and be distributed as to mechanism of the present invention.Additionally, use equally embodiments of the invention, and support media-independent with the signal of particular type that be used for to carry out this distribution.The example that signal supports media comprises: but for example recording medium of storage card, CD and disk, hard drives and for example transmission medium of Digital and analog communication link.

[00111] in the situation that do not break away from basic instruction, various other changes and improvements can be implemented based on the structure of illustrating here and technology.Therefore, be provided for detecting and/or quantizing to measure numerous systems, equipment and the method for electric capacity.Although stated at least one example embodiment in the detailed instructions in front, should be understood that to have a large amount of modification.For example, each step of technology described here can be implemented with temporary transient order, is not limited to the order of stating and/or stating here.It is to be further understood that exemplary embodiments described here only is example, be used for never in any form limiting the scope of the invention, application or structure.Therefore, in situation about not breaking away from such as the scope of the present invention in attached claims and legal equivalents thereof, set forth, can and arrange and make various changes in the function of parts.

Claims

1. one kind is used for measuring the method that can measure electric capacity, and the method comprising the steps of:

Use the first switch that voltage is applied to and to measure electric capacity;

Permission can be measured electric capacity and be shared electric charge with passive network;

If the electric charge on the passive network surpasses threshold value, then the electric charge on the passive network is changed the electric charge of quantized amount, described threshold value provides the reference voltage to quantizer; With

Repeating each applies step, allows step and changes step at least one times.

2. according to claim 1 method is wherein saidly executed alive step and is comprised and apply predetermined voltage, and the electric charge of described quantized amount is based on this predetermined voltage.

3. according to claim 1 method further comprises, at least part of multiplicity based on changing step determines to measure the step of capacitance.

4. according to claim 1 method, the multiplicity that wherein applies step is not equal to the multiplicity that changes step.

5. according to claim 1 method wherein changes step and comprises the electric charge that repeatedly changes on the passive network.

6. according to claim 1 method is wherein repeatedly carried out and is applied each time repetition that step is used for changing step, and repeatedly carries out each time repetition that allows step to be used for the change step.

7. according to claim 1 method wherein applies step and comprises the output pin that encourages digital control circuit.

8. according to claim 1 method, the electric charge of the quantized amount that wherein changes at passive network is corresponding to the electric charge on the feedback capacity.

9. according to claim 1 method, the electric charge of the quantized amount that wherein changes at passive network is corresponding to the electric current of the known a period of time that applies by resistance.

10. according to claim 9 method wherein applies electric current by applying second voltage at the resistance two ends.

11. method according to claim 1 further comprises the steps: multiplexedly between the electric capacity to apply step, allow step and change step a plurality of the measurement, wherein can measure electric capacity is a plurality of one of electric capacity of measuring.

12. method is according to claim 1 wherein only carried out with switch and passive element and is applied and allow step.

13. method according to claim 12, wherein switch comprises the numeral output of controller.

14. method according to claim 1 wherein carries out applying, allowing and change step with the digital input and output of controller.

15. method according to claim 1, the threshold voltage of wherein inputting by the numeral of controller comes definite threshold.

16. method is according to claim 1 wherein come definite threshold by analog-to-digital converter.

17. method according to claim 1 wherein applies step and comprises and charging to measuring electric capacity, and changes step and comprise from passive network and remove electric charge.

18. method according to claim 1 wherein applies step and comprises and discharging to measuring electric capacity, and changes step and comprise to passive network and add electric charge.

19. method according to claim 1 wherein allows step to comprise that passive license can measure electric capacity and use sharing circuit to share electric charge with passive network, and applies step and basically occur soon than the time constant of sharing circuit.

20. method according to claim 1 wherein allows step to comprise the control second switch.

21. method according to claim 1 further comprises step:

A plurality of charge values that quantized on the passive network are stored in the storer; With

To this a plurality of value Applied Digital filtering.

22. method according to claim 1 further comprises protection voltage is applied to the step that is different from the guard electrode that can measure electric capacity.

23. method according to claim 22, the protection voltage that wherein imposes on guard electrode during applying step is substantially equal to impose on the voltage that can measure electric capacity during applying step.

24. method according to claim 22, the protection voltage that wherein imposes on guard electrode is substantially equal to can measure the voltage on the electric capacity after allowing step.

25. method according to claim 22 wherein approaches the variation that is applying and allowing can measure between the step voltage on the electric capacity in the variation that applies and allow to impose between the step protection voltage of guard electrode.

26. one kind is used for measuring the system that can measure electric capacity, this system comprises:

Be used for using the first switch that voltage is repeated to impose on the device that can measure electric capacity;

Be used for repeating to allow to measure electric capacity is shared electric charge with passive network device; With

If the electric charge that is used on the passive network surpasses threshold value, the loading that then passive network powered on changes the device of some electric charges again, and described threshold value provides the reference voltage to quantizer.

27. one kind is used for measuring the circuit that can measure electric capacity, this circuit comprises:

The first switch, it is coupled to can measure electric capacity;

Passive network, it is coupled to can measure electric capacity, and wherein passive network is configured to store the electric charge that receives from measuring electric capacity; With

The charge variation circuit, it is coupled to passive network; With

Controller, it is configured to by using the first switch to repeat to apply voltage to measuring electric capacity, the electric charge repeated storage that will receive from the electric capacity measured on the passive network, and response surpasses electric charge on the passive network of threshold level, utilizes the charge variation circuit electric charge on the passive network repeatedly to be changed the electric charge of some, thereby determines to measure the numerical value of electric capacity.

28. circuit according to claim 27, wherein said voltage is predetermined voltage, and amount of charge is based on predetermined voltage.

29. circuit according to claim 27, wherein said voltage are supply voltage.

30. circuit according to claim 27, wherein passive network comprises capacitor.

31. circuit according to claim 27, wherein the first switch is the numeral output of controller.

32. circuit according to claim 31 further comprises second switch, described second switch is coupled to electric charge and changes circuit and passive network, and wherein second switch operationally changes the electric charge on the passive network electric charge of some.

33. circuit according to claim 31 further comprises the 3rd switch, described the 3rd switch is coupled to can measure electric capacity and passive network, and wherein the 3rd switch operationally allows to measure electric capacity and shares electric charge with passive network.

34. circuit according to claim 27 further comprises second switch, described second switch is coupled to can measure electric capacity and passive network, and wherein second switch operationally allows to measure electric capacity and shares electric charge with passive network.

35. circuit according to claim 30, wherein passive network comprises resistance.

36. circuit according to claim 27 further comprises the tension measuring circuit that is coupled to passive network.

37. circuit according to claim 36, wherein tension measuring circuit comprises comparer.

38. circuit according to claim 36, wherein tension measuring circuit comprises analog-to-digital converter.

39. circuit according to claim 36, wherein tension measuring circuit comprises the input threshold value of the numeral input of controller.

40. circuit is according to claim 39 wherein inputted threshold value and is had hysteresis.

41. circuit according to claim 27 further comprises the signal pin of controller, this signal pin is coupled to can measure electric capacity, and its middle controller is configured to via this signal pin voltage be imposed on can measure electric capacity.

42. circuit according to claim 27 further comprises second switch and the 3rd switch, wherein passive network comprises:

The first capacitor, it is coupling in the 3rd switch and can measures between the electric capacity; With

The second capacitor, it is coupling between the first switch and the second switch.

43. circuit according to claim 27 further comprises second switch, wherein passive network comprises:

Be coupling in the first capacitor between the first switch and the second switch; With

Be coupled to the first switch and the resistance that is coupled to second voltage; With

Be coupled to the resistance of second voltage.

44. circuit according to claim 27, wherein passive network comprises and is coupled in series to mutually capacitor the first switch and that be coupled to second voltage and resistance.

45. circuit according to claim 27 further comprises second switch and the 3rd switch, wherein passive network comprises:

Be coupling in the 3rd switch and can measure capacitor between the electric capacity; With

Be coupling in the resistance between the first switch and the second switch.

46. circuit according to claim 45 is further configured to by excitation second switch certain hour section and changes electric charge on the passive network, thereby allows the electric charge on the passive network to pass through resistance.

47. circuit according to claim 27 further comprises guard electrode, its middle controller is further configured to protection voltage is imposed on guard electrode.

48. circuit according to claim 47 further comprises the impedance divider, it is coupled to second switch and guard electrode.

49. circuit according to claim 47 wherein drives guard electrode by digital to analog converter.