Design Of A Multifunctional Infrared Focal Plane Readout Circuit

Infrared detection imaging technology has been widely used in military and civilian fields because of its low cost,small size,strong anti-interference ability and many other advantages.Readout Integrated Circuit(ROIC)is the core module in the infrared detector system,and highperformance readout circuit is the premise of obtaining high-quality imaging.At the same time,with the continuous improvement of materials,processes and devices in the field of infrared detection,the readout circuit is developing in the direction of larger area array,more functions and more intelligence,so the research on new readout circuits is very important.Aiming at the single function of the traditional focal plane readout circuit,this paper designs a multifunctional infrared focal plane readout circuit,which can realize ordinary sunlight/low light infrared imaging,laser pulse detection and two-dimensional infrared imaging in the same pixel by using a mode switch.Four functions for distance measurement.Regarding the laser pulse detection function,the text constructs a threshold detection circuit with a resistive feedback transimpedance amplifier(RTIA)as the core.For practical application scenarios,a feedback loop is innovatively added to the traditional RTIA structure,which can effectively Filtering out the low-frequency direct current introduced by the background ambient light signal not only improves the detection sensitivity of the circuit but also reduces the transmission delay.As for the two-dimensional ranging function,the indirect photon time-of-flight(TOF)measurement method based on time-to-amplitude converter(TAC)is used,and the above-mentioned pulse detection structure and ramp generation are cascaded using the idea of circuit structure multiplexing.The circuit and sample-hold module can realize highprecision TOF measurement,and cleverly complete the integration of four functions in a small pixel area.In this paper,the design and simulation verification of the multi-function readout circuit is completed based on the TSMC 180 nm CMOS process.The array scale is 64 × 64,and the pixel area is 30 μm × 30 μm.The chip was taped out for engineering batches in November 2021,but due to the tight production capacity of the tape-out foundry in recent years,the chip has not been offline at present,so chip-level testing cannot be completed.In this paper,the system-level simulation and postlayout simulation verification of the chip are carried out.The post-simulation results show that the system can normally achieve the above four preset basic functions.The output swing of the infrared imaging circuit reaches 3.14 V,and the dynamic range in the high and low gain modes is 58.07 d B and68.22 d B respectively,and the linearity is The amplitude sensitivity of the laser pulse detection circuit is 0.5μA,and the pulse width sensitivity is 0.9ns;the circuit of the laser two-dimensional ranging based on TAC functions well,and the slope of the signal at the ramp time base is 1.3979 V In the case of /μs,TOF can reach a detection range of 2μs and a resolution of 1.97 ns.