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Capacitance-to-digital interface circuit for differential pressure sensor

  • US 7,324,029 B2
  • Filed: 01/26/2006
  • Issued: 01/29/2008
  • Est. Priority Date: 01/26/2006
  • Status: Active Grant
First Claim
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1. A two-phase, second order capacitance-to-digital (CD) modulator for converting a first capacitance CX and a second capacitance CY to a pulse code modulated (PCM) signal representative of (CX

  • CY)/(CX+CY), the CD modulator comprising;

    a first stage sigma-delta integrator for selectively forming charge packets in CX and CY during a first phase, and integrating charge from CX and CY during a second phase to produce a first stage output VOUT1, wherein the first stage sigma-delta integrator holds VOUT1 constant during the first phase;

    a second stage sigma-delta integrator for sampling the first stage output VOUT1 during the first phase, and integrating the sampled first stage output during the second phase to produce a second stage output VOUT2; and

    a quantizer for converting the second stage output VOUT2 to the PCM signal.

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