一种应用于短波红外焦平面的大动态范围像素级ADC

A Wide Dynamic Range Pixel Level ADC for Short-Wave IRFPA

摘要:

针对短波红外焦平面的大动态范围需求,设计了一种像素级脉冲频率调制(PFM)模数转换器(ADC)。传统PFM ADC采用DI输入级,进行弱信号探测时,注入效率会下降,造成动态范围的损失。设计的PFM ADC采用CTIA输入级,弱信号探测时仍能维持高注入效率；同时采用两档增益和增益自选择技术,使得每个像素都能够根据输入的光电流自动选择增益,在提升动态范围的同时,不增加额外的功耗。在0.18μm CMOS工艺模型下,仿真结果表明该电路的动态范围达到100.1dB,单元ADC功耗小于10.54μW,并且基于所设计的改进型PFM ADC设计了规模为32×32、中心距为50μm的像素级数字化读出电路。

Abstract:

In this paper, a pixel level pulse-frequency-modulation (PFM) ADC was designed for the wide-dynamic-range short infrared focal plane array (IRFPA). When the conventional PFM ADC uses DI to detect weak signal, the injection efficiency will decrease, which result in the loss of the dynamic range. In the designed PFM ADC, the CTIA is used to maintain high efficiency when detecting weak signal. Two levels of gain and self-selected gain technology are used to extend the dynamic range without increasing the power consumption. Self-selected gain technology enables each pixel to choose the gain according to the photocurrent automatically. The circuit was designed and simulated with 0.18μm CMOS process model. The dynamic range is up to 101.5dB,and the power consumption of each pixel is only 10.54μW. A 32×32 pixel level digital readout circuit with the pixel pitch of 50μm was designed based on the proposed PFM ADC.