High Dynamic Range Pinned Photodiode Pixel with Floating Gate Readout and Dual Gain

Stefanov, Konstantin and Prest, Martin J. (2023). High Dynamic Range Pinned Photodiode Pixel with Floating Gate Readout and Dual Gain. In: 2023 International Image Sensor Workshop, 21-25 May 2023, Crieff, Scotland.

URL: https://imagesensors.org/2023-international-image-...

Abstract

This paper presents a pixel based on the pinned photodiode (PPD) with high dynamic range achieved via in-pixel dual conversion gain. The pixel operates with a single exposure and a single charge transfer out of the PPD. The signal charge is first converted to voltage non-destructively with low gain using capacitive coupling to a floating gate. A second conversion with high gain follows at a pn junction-based sense node after another charge transfer. An increased dynamic range is achieved due to the sensing of the same charge with two different conversion gains. The results from a prototype 10 μm pitch pixel, manufactured in a 180 nm CMOS image sensor process, demonstrate conversion gain ratio of 3:1, dynamic range of 93.5 dB, 2.4 e⁻ RMS readout noise, and negligible image lag. The pixel can operate in global shutter mode with the same low noise as in rolling shutter due to the intermediate signal storage under the floating gate.

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