The Key Techniques Research On CMOS-TDI Image Sensor Based On Hybrid Charge-digital Accumulation Architecture

The CMOS-TDI image sensor can be classified into three categories: analog domain,digital domain and charge domain,according to the location where the signal is accumulated.In order to reduce the noise level and expand the saturation level simultaneously,a hybrid accumulation architecture based on charge domain and digital domain accumulation schemes is proposed.The key techniques of CMOS-TDI Image Sensor based on hybrid charge-digital accumulation architecture has been researched in this paper.An analytical model of hybrid accumulation architecture based on charge-digital accumulation CMOS-TDI image sensor is established.Signal-noise-ratio,dynamic range,and modulation transfer function is simulated and analyzed.The synthetical evaluation target(SET)is defined to obtain the best performance.Then we have researched the CMOS charge transfer pixel and digital readout circuit separately.Simulation has been performed to CMOS charge transfer pixel with the aid of TCAD,the influence of operating voltage and gap size to the charge transfer efficiency and full-well capacity.A two-step prediction architecture has been adopted to the digital readout circuit.The digital readout circuit including DPGA,SAR ADC and PTAT current source and reference voltage have been designed.According to the MATLAB simulation results,the hybrid accumulation scheme whose charge-domain accumulation stage is 8 and digital domain accumulation stage is 16 has the optimal SET,which is 12.99% higher than a 128-stage digital-domain accumulation scheme and 25% higher than the 128-stage charge-domain accumulation scheme.Charge transfer efficiency achieves 99.999% and the well capacity reaches up to 25,000 electrons for gap size of 130 nm and maximum operating voltage of 3V according to the TCAD.The charge transfer pixel has been tape out and the digital readout circuit is designed and simulated based on the 0.13 ?m CMOS standard process.