US Patent 7142138 Multi-step analog/digital converter and on-line calibration method thereof

The present invention discloses an on-line calibration method, which utilizes two calibration algorithms running in the background without interrupting the normal operation of the analog signal process. The method includes performing a residue amplifier gain error calibration and performing a DAC non-linearity calibration. The residue amplifier gain error calibration can reduce the gain error of the residue amplifier for a missing code or a missing decision level phenomenon. The DAC non-linearity calibration can relax the matching requirement of passive components in current semiconductor processes. The present invention discloses a two-step ADC (Analog-to-Digital Converter), which includes a first signal processing unit, a second signal processing unit, a programmable gain control unit and a programmable reference voltage generator, performing the on-line calibration method.