超高行频高灵敏度短波红外焦平面读出电路研究

Research on ultra-high line frequency high sensitivity short-wave infrared focal plane readout circuit

摘要:

针对食品色选以及医疗成像的应用,设计了一款短波红外InGaAs焦平面用高行频高灵敏度1024×1元线列读出电路。读出电路输入级采用CTIA结构,具有较高的注入效率的特点,针对微光、强光等不同应用场景,设计4档积分电容,最高增益档积分电容为10 fF。研究单元电路输出级瞬态响应,优化开关管尺寸、设计高带宽运放以减小关键节点时间常数,进而降低输出级运放噪声,提高动态范围。优化读出电路版图电源网络,抑制功耗过高引起的压降问题。经标准CMOS 0.18 μm工艺开展读出电路加工,并与像元中心距12.5 μm光敏芯片匹配耦合, 读出电路采用边积分边读出(IWR)工作模式。结果表明,1024×1元线列焦平面功耗118.8 mW ,动态范围71dB,噪声小于0.52 mV,实现40 kHz超高行频读出。

Abstract:

For the application of food color sorting and medical imaging, a high line frequency high sensitivity 1024×1-element line column readout circuit was designed for short-wave infrared InGaAs focal plane. The input stage of the readout circuit adopts CTIA structure, which has the characteristics of high injection efficiency, and is designed with 4 levels of integrated capacitance for different application scenarios such as low light and strong light, and the highest gain level of integral capacitance is 10 fF. The transient response of the output stage of the unit circuit is studied, the switch size is optimized, and the high-bandwidth op amp is designed to reduce the time constant of the key node, so as to reduce the noise of the output stage op amp and improve the dynamic range. Optimize the readout circuit layout power supply network to suppress the voltage drop caused by excessive power consumption. The readout circuit is processed by the standard CMOS 0.18 μm process, and is coupled with a photosensitive chip with a pixel center distance of 12.5 μm. The readout circuit adopts the Integral While Readout (IWR) operation mode. The results show that the power consumption of the 1024×1-element line focal plane is 118.8 mW, the dynamic range is 71dB, the noise is less than 0.52 mV, and the ultra-high line frequency readout of 40 kHz is realized.