A Cryogenic Readout IC with 100 KSPS in-Pixel ADC for Skipper CCD-in-CMOS Sensors

TL;DR

This paper presents a cryogenic readout integrated circuit with a 100 KSPS in-pixel ADC designed for Skipper CCD-in-CMOS sensors, enabling high-speed, low-noise, and low-power imaging at 100 Kelvin.

Contribution

The paper introduces a novel 65 nm CMOS-based readout IC with in-pixel ADC for Skipper CCD-in-CMOS sensors, achieving high sampling rate and low noise at cryogenic temperatures.

Findings

Achieves 100 KSPS sampling rate with 0.48 e- RMS noise.

Operates at 100 Kelvin with 40 μW power per pixel.

Maximum dynamic range of 9,000 e- at lowest gain.

Abstract

The Skipper CCD-in-CMOS Parallel Read-Out Circuit (SPROCKET) is a mixed-signal front-end design for the readout of Skipper CCD-in-CMOS image sensors. SPROCKET is fabricated in a 65 nm CMOS process and each pixel occupies a 50$\mu$m $\times$ 50$\mu$m footprint. SPROCKET is intended to be heterogeneously integrated with a Skipper-in-CMOS sensor array, such that one readout pixel is connected to a multiplexed array of nine Skipper-in-CMOS pixels to enable massively parallel readout. The front-end includes a variable gain preamplifier, a correlated double sampling circuit, and a 10-bit serial successive approximation register (SAR) ADC. The circuit achieves a sample rate of 100 ksps with 0.48 $\mathrm{e^-_{rms}}$ equivalent noise at the input to the ADC. SPROCKET achieves a maximum dynamic range of 9,000 $e^-$ at the lowest gain setting (or 900 $e^-$ at the lowest noise setting). The circuit operates at 100 Kelvin with a power consumption of 40 $\mu W$ per pixel. A SPROCKET test chip was submitted in September 2022, and test results will be presented at the conference.