A 320×256 readout integrated circuit (ROIC) with a pixel pitch of 30μm is presented for solar-blind AlGaN ultraviolet focal array plane (FPA). Capacitor feedback transimpendance amplifier (CTIA) has been selected as the input structure of the ROIC because of its excellent performance. A novel cascade amplifier with a symmetrical differential input stage is designed for input stage of CTIA, and an ultra-low capacitance with a value of 10fF is in the feedback loop of the amplifier as integral capacitor. Furthermore, the ROIC read out in a rolling shutter mode by using cascade D flip-flops. The ROIC has been fabricated 0.35μm 2P4M mixed signal CMOS process and interfaced with AlGaN solar-blind ultraviolet focal array plane (UVFPA). The test result shows that 320×256 AlGaN UVFPA has a wide dynamic range of 88.2dB with 5V power supply and has a high injection efficiency of 98.2%.
To meet the desire of radiation-hardened Electro-Static Discharge (ESD), a series of ESD protection devices and structures were proposed for ultraviolet (UV) AlGaN focal plane arrays (FPAs) readout circuit in this paper. The whole-chip ESD protection structures for I/O pads and power clamp (PC) pads fabricated in Global Foundries 0.35μm 2P4M mixed signal process are investigated. The structure-level and layout-level radiation hardened technologies are used to solve the problem of ESD current discharge efficiency and radiation hardened. Experimental results were obtained by transmission line pulse (TLP) testing system before and after the radiation hardening, it shows that the proposed ESD protection structures can reach the Human Body Model(HBM) ESD level to more than 4kV, while the total dose of ionizing radiation(TID) was 50krad (Si). Moreover, the whole chip ESD protection network are separated into logic ESD protection modules and analog ESD protection modules respectively to decrease crosstalk effect, and multi power clamp ESD protection devices are placed to improve the ESD current discharge efficiency.
A novel column-stage structure of readout integrated circuit (ROIC) for GaN ultraviolet (UV) focal plane array (FPA) working in “solar-blind” band is proposed. The column stage has better drive capability, higher dynamic range, stable bias current and low impedance. The noise voltage of the column readout stage is discussed, which has been reduced by small-current driving, column-stage sample and hold and the technology of divided-output-bus. This research on low-noise ROIC is designed for weak-current UV FPA. It is designed, simulated and laid out using the 0.35um 2P4M CMOS 5V process. The clock rate operates at 8MHz. The simulation input current sets 0.01nA. The output swing is 2.6V and power consumption is 40 mW according to the measurement results.