High-Speed, High Dynamic-Range Optical Sensor Arrays

A monolithic solid-state linear sensor array has been designed and fabricated in a 0.35 mum , 3.3 V, thin-oxide digital CMOS process. The sensor arrays are targetted at such instruments and applications as digital streak cameras, 2-D cameras for proton radiography, and fiber-optic array readout. The prototype consists of a 1-D linear array of 150 integrated photodiodes, followed by fast analog buffers and on-chip, 150-deep analog frame storage. Frame storage consists of 150 analog sample circuits per pixel, with each sample circuit including an n-channel sample switch, a 0.1 pF double-polysilicon sample capacitor, a reset switch to clear the capacitor, and a multiplexed source-follower readout buffer. Sampling speeds of 400 M-frames/s have been achieved using electrical input signals, and 100 MHz with optical input signals, both with a dynamic range of ~ 11.5 bits, rms. Circuit design details are presented, along with the results of electrical measurements and optical experiments with fast pulsed laser light sources at several wavelengths. A set of next-generation concept designs are also presented that aims to include PLL-based clock multiplication for 1 GHz continuous sampling, plus a new real-time trigger circuit technique that examines windowed regions of stored samples to form a sophisticated trigger decision.