US Patent 7129875 Tracking reference system for analog-to-digital converter systems

An analog-to-digital (A/D) converter system is provided that compensates for operating variations associated with one or more passive components of the A/D converter. In one aspect of the present invention, the A/D converter system comprises a sigma delta modulator having at least one passive component and a feedback path that includes at least one switched digital-to-analog converter (DAC), and a tracking reference generator that provides compensated reference signals to the at least one switched DAC for providing feedback to the sigma delta modulator. The compensated reference signals include inverse variations that cancel operating variations associated with the at least one passive component.