A Low Noise Single-Slope ADC with Signal-Dependent Multiple Sampling Technique

Abstract

A low noise single-slope analog-to-digital converter (SS-ADC) is presented employing a signal-dependent multiple sampling scheme for low-light imaging and high-accuracy ranging. The SS-ADC adopts multiple ramps to convert the signal of a pixel several times to average out random noise of readout circuits, improving a signal-to-noise ratio without any penalty on a readout time. The prototype SS-ADC fabricated in standard 0.11 μm CIS process with an indirect time-of-flight pixel array improves a depth accuracy up to about 40% at a long distance.