二极管型红外探测器数字输出型读出电路

Diode infrared detector ROIC with digital output

摘要:

为实现红外焦平面数字化输出,设计了一款片上集成行列级读出电路,适应于SOI（silicon on insulator）二极管型非制冷红外探测器阵列.读出电路包括一个连续时间增量型二阶sigma-delta调制器和一个输出缓冲器,其中二阶sigma-delta调制器包括跨导模块、跨导运算放大器构成的积分器模块、电流型DAC反馈模块以及比较器.基于此提出的读出电路架构,采用直接数字量化的方式,完全省去了前端模拟放大单元电路.利用连续时间增量型二阶sigma-delta调制器对输入信号驱动要求低的特点,该电路可直接处理SOI二极管型红外探测器输出的相对微弱的电压信号,并输出数字信号.基于SMIC 0.35 μm CMOS工艺对电路进行了设计并流片验证,供电电压5 V,读出电路版图通道宽度小于30 μm,适应探测器像素尺寸.测试结果表明, 60帧频读出时,读出性能良好,输出噪声9 μV,单通道功耗450 μW,面积0.092 mm².该读出电路相比于普通片上集成行列级读出电路,减小了面积和功耗,简化了整个红外成像系统,适用于低功耗、低噪声、高集成度的大面阵数字化红外传感器成像系统.

Abstract:

A line readout circuit with digital outputs is presented in this paper, which is suitable for SOI diode uncooled infrared focal plane arrays. The readout channel consists of a second-order sigma-delta modulator and an output buffer. The modulator includes an integrator, a current DAC, and a comparator. With the proposed circuit desiqn which adopts direct digital guantification, traditional analog pre-amplifier circuits are no longer needed. Continuous time increment type sigma-delta modulator can be driven by weak signals, which is capable of dealing with relatively small signals outputted by SOI diodes. The readout circuit was designed and simulated with 5 V supply voltage and the readout channel width was limited below 30 μm to meet the requirement of pixel physical size. The tape-out was completed in SMIC 0.35 μm CMOS technology to further validate the effectiveness of this design. Test results show that the output noise was less than 9 μV with 60 Frame/s under room temperature, the power consumption of each channel was less than 450 μW with 5 V power supply voltage, and the area of each channel was 0.092 mm² . Compared with traditional readout circuits, the proposed circuit needs no pre-amplifier circuits nor off-chip ADC, which reduces the complexity of the system. This design can be used in low power, low noise, and high density large scale infrared imaging systems with less chip area and power consumption.