New on-chip analog-to-digital conversion circuit for IRFPA

A new type of pixel-level on-chip analog-to-digital conversion circuit for infrared focal plane array (IRFPA) has been proposed based on serial single-slope integration. An 8×8 pixel array readout circuit chip has been designed. The layout design and circuit simulation of the chip are also been completed. In each pixel, the current signal is inputted through a data input (DI) injection circuit and outputted as a series of digital pulses proportional to magnitude of input current. Then these digital pulses are counted by the counter which shared by each column pixel. With the unique sharing structure and compensation technique of injected charge, this circuit shows many advantages, including simple structure and small area. Simulation result shows that this chip can realize signal readout and A/D conversion of IRFPA. Each pixel has an area of 80 μm× 80 μm and average power consumption of 50 μW. Simulation and; test results show that the quantized resolution of this circuit is 8 bit and quantized error is less than 4 LSB. Frame rate reaches up to 460 f/s.