An oximeter uses a sigma-delta modulator and a multi-bit ADC with PWM feedback enabling high precision multi-bit conversion. Demodulation is done in software, thus requiring only a single hardware path for both red and IR. Multiple capacitors are switched into the integrator in the sigma-delta modulator,...http://www.google.de/patents/US7142142?utm_source=gb-gplus-sharePatent US7142142 - Multi-bit ADC with sigma-delta modulation
