Abstract: An analogue to digital converter (ADC) of the recirculating type is described. In one embodiment, the ADC is composed of three storage and residual determination units, which, in cooperation with an operational amplifier, and suitable comparator means, are operable to re-present residual signals for analogue to digital conversion. To enhance settling at the beginning of a cycle, the first storage and residual determination unit is used once, with remaining recirculation being conducted between the other two storage and residual determination units. Another embodiment presents a recirculating ADC stage which comprises a plurality of capacitor banks operable to be switched into and out of connection with other components of the ADC stage, in order to recirculate residual values for calculation of further bits of a digital output. Each bank comprises a plurality of capacitors, and cooperating switching means for connecting each bank in turn with the other components.

Abstract: An integrated analog to digital interface subsystem for imaging applications includes digital global and digital pixel by pixel offset correction and scaling. The integrated interface 2 includes 3 DAC's 2c1-2c3 that are used to do a rough offset cancellation on the three analog input signals (RGB) in the analog domain. A triple sample/hold circuit 2a samples the RGB signals simultaneously, multiplexes the data and passes the three signals on the ADC 2b sequentially (at about 3 times the data rate). The sample/hold circuit 2a has the capability to operate in fully differential as well as single ended input mode, and can perform correlated double sampling if needed. A high resolution ADC 2b converts the 3 multiplexed signals from simple/hold circuit 2a. A first digital offset correction circuit 2f restores the level of the RGB signals in the digital domain on a pixel by pixel basis.