A 40mW/channel Image Sensor Line Driver IC with Independently Tunable Gain and Settling Time

Abstract

A 16-channel analog front-end integrated circuit (IC) for interfacing an image sensor with single-ended analog output to a differential-input digitizer is presented. The IC is designed for image sensors used in single-electron counting direct detection cameras with applications in cryogenic electron microscopy (cryo-EM), but it’s high flexibility allows usage with a variety of sensors. An operational transconductance amplifier (OTA) and a transimpedance amplifier (TIA) replace the traditional instrumentation amplifier, to allow power reduction and decoupling of the gain and bandwidth stages. This allows for a tunable gain in order to exploit the digitizer full-scale range, and an independent bandwidth tuning capability to accommodate a variety of sensors. Additionally, the front-end supports a very wide input common-mode range, and provides offset correction capability as well as frame marker operation. The chip is fabricated in a commercially available 180nm CMOS technology using dual 3.3V/1.8V supply. It achieves more than ±10% gain tunability at 0-1.2V sensor dark-level range, and up to 142MHz operation. Power consumption is measured at 37mW/channel with 155µV input-referred noise, at nominal conditions. The chip is a low-power, low-noise, highly optimized solution allowing area and power reduction in camera assemblies.