Patent ID: 9380208
Filing Date: 2016-06-28
CPC Classification: H04N

Claim Text:
1. A ramp generator for use in readout circuitry of an image sensor, comprising: a supply voltage sampling circuit coupled to a pixel cell of the image sensor to sample a black signal supply voltage of the pixel cell during a black signal readout of the pixel cell, and to sample an image signal supply voltage of the pixel cell during an image signal readout of the pixel cell; a first integrator circuit having a first input coupled to receive a buffered reference voltage, and a second input coupled to an output of the supply voltage sampling circuit; a first switch coupled between the first input of the first integrator circuit and a first capacitor; a second switch coupled between an output of the first integrator circuit and the first capacitor, wherein the first and second switches are switched to transfer a signal representative of a difference between the image signal supply voltage and the black signal supply voltage to the first capacitor; and a second integrator circuit coupled to the first capacitor, wherein the second integrator circuit is coupled to generate an output ramp signal coupled to be received by an analog to digital converter, wherein a starting value of the output ramp signal is adjusted in response to the difference between the image signal supply voltage and the black signal supply voltage.