Managing power consumption by sampling circuit current sources

Abstract

An image sensor includes a plurality of pixel sensors arranged in at least one row and a plurality of columns. Each pixel sensor includes a photosensor to generate a photosensor output signal nominally indicative of an intensity of light incident on the photosensor. Each pixel sensor is configured to provide a signal corresponding to the photosensor output signal at an output of the pixel sensor. For each column, a column line couples together the outputs of the pixel sensors belonging to that column and terminates in a column node for that column. Column output circuitry associated with each column provides to image sensor sampling circuitry a signal corresponding to the column node for that column, based on an asserted state of a column enable signal for that column. Power consuming circuitry is associated with each column and is controllable between at least a normal power mode and a minimal power mode such that, when the power consuming circuitry associated with a particular column is in the minimal power mode, signals representing photosensor output signals generated by photosensors of that column's pixel sensors are prevented from being reliably sampled by the image sensor sampling circuitry. Controller circuitry coordinates the control of the power mode of the power consuming circuitry associated with each column with the state of the column enable signal for that column.