Global shutter image sensor with anti-blooming pixel and knee point self-calibration

Abstract

An image sensor has global shutter imaging pixel cells, each including an anti-blooming transistor gate for modifying electric charge within a photodiode and for setting the photodiode to a selected potential. The sensor also has a row decoder circuit providing readout signals to each row of the imaging cells during both a readout interval and during a calibration interval for each row and providing to the anti-blooming transistor drain a selectable potential supply voltage. A mode select switch within the row decoder circuit applies either a standard drain supply voltage or an adjustable low voltage to the anti-blooming transistor drain. A programmable function logic circuit determines the timing of operation of the mode select switch to provide knee-point calibration to minimize photo conversion variations that lead to fixed pattern noise.