Frame-wise calibration of column-parallel adcs for image sensor array applications

Abstract

Circuits, methods, and apparatus are described that provide calibration of column-parallel analog-to-digital converters (ADCs) in image processing contexts only once per frame (or less frequently) to reduce column-wise noise. For example, the column ADCs are calibrated during an inter-frame time interval, like a vertical blanking interval. In some embodiments, calibration data for the column ADCs for a calibration period is stored at the digital block for use in processing row data from the column ADCs. In other embodiments, calibration data for the column ADCs for the calibration period is stored at column ADCs in a local memory for local correction of the pixel data prior to being read out to the digital block for processing. In certain embodiments, techniques, such as differential ADC architectures, are used to mitigate row-wise noise in context of the frame-wise calibration.