A 4-channel 20-to300 Mpixel/s analog front-end with sampled thermal noise below kT/C for digital SLR cameras

We present a 4-channel analog front-end (AFE) designed specifically for multichannel sensors used in digital single-lens reflex (DSLR) cameras. Multichannel sensors have been adopted as a solution to the increasing requirements for higher throughput in imaging systems. Single-channel AFEs have been published; however, there are drawbacks to using multiple discrete single-channel AFEs in a multichannel system. For example, column readout patterns are particularly sensitive to mismatch between AFE channels. Also, DSLR cameras support many different frame capture modes and read-out patterns, requiring clock rates from below 10MS/s to over 70MS/s, and previous AFEs have not been designed to operate over such a wide range. This paper describes several design techniques developed for the DSLR application, including adaptive power scaling, an integrated reference buffer, and a low-noise sampling technique with sampled thermal noise below kT/C.