Charge leakage compensation in analog-to-digital converter

An apparatus comprising:

• a photodiode configured to generate charge responsive to incident light;
• a capacitor configured to store charge generated by the photodiode to develop a voltage;
• a reference generator configured to output a reference signal;
• and
• an analog-to-digital converter (ADC) circuit, comprising:
• a quantizer;
• and
• a leakage compensation circuit configured to:
• receive an input signal derived from the voltage, the input signal being susceptible to a drift due to a charge leakage via an input terminal of the quantizer;
• receive the reference signal;
• generate a leakage-compensated signal pair to compensate for the charge leakage, wherein the leakage-compensated signal pair comprises one of:
• (a) a leakage-compensated version of the input signal and the reference signal,
• (b) the input signal and a leakage-compensated version of the reference signal, or
• (c) a leakage-compensated version of the input signal and a leakage-compensated version of the reference signal,
• wherein the quantizer configured to perform a leakage-compensated quantization of the input signal based on the leakage-compensated signal pair to generate a digital output representing the voltage.

A method comprising:

• receiving, by a leakage compensation circuit, an input signal, the input signal being susceptible to drift due to charge leakage via an input terminal of a quantizer;
• receiving, by the leakage compensation circuit, a reference signal;
• generating, by the leakage compensation circuit, a leakage-compensated signal pair to compensate for the charge leakage, wherein the leakage-compensated signal pair comprises one of:
• (a) a leakage-compensated version of the input signal and the reference signal,
• (b) the input signal and a leakage-compensated version of the reference signal, or
• (c) a leakage-compensated version of the input signal and a leakage-compensated version of the reference signal;
• and
• performing, by the quantizer, a leakage-compensated quantization of the input signal based on the leakage-compensated signal pair to generate a digital output representing the input signal.