Stmicroelectronics (Grenoble 2) Sas

Stmicroelectronics R&d Limited

Stmicroelectronics Sa (Morocco)

Mhamed El Hachimi

Laurent Simony

Graeme Storm

Matthew Purcell

Derek Tolmie

Min Qu

An image sensor has a per-column ADC arrangement including first and second capacitors allowing a comparator circuit to perform correlated double sampling. The capacitors are continuously connected to, respectively, the analog pixel signal and a ramp signal without use of a hold operation. The comparator circuit comprises a differential input being connected to the junction of the two capacitors and being biased by a reference signal. The reference signal is preferably sampled and held from a reference voltage. The use of a differential input as first stage of the comparator addresses problems arising from ground voltage bounce when a large pixel array images a scene with low contrast. Connectivity of the differential input stage allows the ramp signal to see a constant capacitive load thus reduce image artifacts referred to as smear.

Analog-to-digital conversion in image sensors

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Edinburgh, United Kingdom

Mhamed El Hachimi