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提出并设计了一种适用于激光3D成像的盖革模式雪崩光电二极管(Geiger-mode avalanche photodiode,GM-APD)阵列像素读出电路。基于飞行时间(time-of-flight,TOF)原理,像素读出电路主要由两部分组成:有源淬火电路(active quenching circuit,AQC)和时间数字转换器(time-to-digital converter,TDC)。所采用的TDC是粗细结合的两段式计数方式,成功实现了时钟频率和时间分辨率间的折中。基于内插技术,由粗计数的线性反馈移位寄存器和细计数的延时线型TDC共同实现了高达18-bit的动态范围。同时两者的时钟频率分别降低至250 MHz和500 MHz,分别是常规设计频率的1/20和1/10,大大降低了设计和应用难度。电路采用SMIC 0.18μm工艺设计,后仿结果显示达到了200 ps的高精度时间分辨率,对应的距离分辨率为3 cm,完全能够满足3 km激光3D成像中的测距要求。像素电路版图面积小于50×95μm2,总功耗为0.89 m W,具有小面积和低功耗的优势。
A Geiger-mode avalanche photodiode (GM-APD) array pixel readout circuit is proposed and designed for laser 3D imaging. Based on the time-of-flight (TOF) principle, a pixel readout circuit mainly consists of two parts: an active quenching circuit (AQC) and a time-to-digital converter (TDC) . The adopted TDC is a two-stage counting method combining the thickness and the thickness, and successfully achieves the trade-off between the clock frequency and the time resolution. Based on the interpolation technique, a coarse count linear feedback shift register and fine count delay line TDC together achieve a dynamic range of up to 18-bit. At the same time, the clock frequency of both is reduced to 250 MHz and 500 MHz respectively, which are respectively 1/20 and 1/10 of the conventional design frequency, which greatly reduces the design and application difficulty. The circuit is designed with SMIC 0.18μm process, and the post-simulation results show that the high resolution time resolution of 200 ps is achieved with the corresponding distance resolution of 3 cm, which can fully meet the ranging requirements of 3 km laser 3D imaging. Pixel circuit layout area of less than 50 × 95μm2, total power consumption of 0.89 m W, with a small area and low power advantages.