Patent ID: 7324029

Claim:
A two-phase, second order capacitance-to-digital (CD) modulator for converting a first capacitance C X and a second capacitance C Y to a pulse code modulated (PCM) signal representative of (C X −C Y )/(C X +C Y ), the CD modulator comprising: a first stage sigma-delta integrator for selectively forming charge packets in C X and C Y during a first phase, and integrating charge from C X and C Y during a second phase to produce a first stage output V OUT1 , wherein the first stage sigma-delta integrator holds V OUT1 constant during the first phase; a second stage sigma-delta integrator for sampling the first stage output V OUT1 during the first phase, and integrating the sampled first stage output during the second phase to produce a second stage output V OUT2 ; and a quantizer for converting the second stage output V OUT2 to the PCM signal.