[54] ANALOG-TO-DIGITAL CONVERTER WITH MULTI-LEVEL DITHER CURRENT INPUT
[75] Inventor: Herbert M. K. Chen, Austin, Tex.
[73] Assignee: Advanced Micro Devices, Inc., Sunnyvale, Calif.
[21] Appl. No.: 126,545
[22] Filed: Sep. 24,1993
[51] Int. CI.* H03M 1/20
[52] U.S. Q 341/131; 341/143
[58] Field of Search 341/131,143,164
[56] References Cited
U.S. PATENT DOCUMENTS 4,354,176 10/1982 Aihara .
5,073,777 12/1991 Fukuhara et al 341/131
5,305,005 4/1994 Nakagawa et al 341/131
An improved sigma-delta analog-to-digital converter (ADC) is disclosed herein. The digital converter includes a dither circuit fabricated within the package of the ADC. The circuit is configured to apply a dither current to the analog input of the ADC. The frequency of the dither current is selected based upon the bandwidth of the analog signals for which the ADC is designed to sample and convert to digital signals. Application of the dither current to the input of the ADC reduces quantization noises produced as a result of certain ranges of DC offset voltages found within analog signals applied to the ADC.
22 Claims, 4 Drawing Sheets
