Development of a Fully Programmable ROIC with 15 mu m Pixel Pitch for MWIR Applications

A 15 mu m pixel pitch 640x512 Readout Circuit (ROIC) for MWIR applications is designed and fabricated using 0.18 um CMOS process. The ROIC is implemented using Direct Injection (DI) input stage with programmable pixel gain where maximum full-well-capacity (FWC) is more than 13Me. All analog current and voltage bias values can be programmed through a digital interface. Additionally, integration time can be programmed with 0.1 mu sec resolution by internal timing circuitry. ROIC has 1, 2 and 4 output modes with a frame rate of 120fps at 4 output mode. The design supports Integrate-Then-Read (ITR) and Integrate-While-Read (IWR) modes in snapshot operation. Photodetector reverse bias voltage is controlled by adjusting the bias of the common-gate input stage at the input of DI pixel. An on-chip low-dropout voltage regulator is used to generate the detector common voltage. With 2x2 binning feature, the ROIC can also be used for 30 mu m pixel pitch 320x256 photodetector arrays. An Analog-Front-End (AFE) card has been designed to operate the ROIC and to convert analog video output to a 14-bit digital value. This digital video data is handled by external video processor card which supports 1-point and 2-point Non-Uniformity Correction (NUC), histogram equalization, bad pixel replacement and filtering. The ROIC has been extensively tested with a prototype FPA at 77 degrees K. According to these test results, functionality of all modes have been verified and a noise level of 700e is achieved at 4.5Me FWC.