Investigation of Transient Dose-Rate Effect on High-Speed Comparator SB9696

Abstract

This paper investigates transient dose-rate effect (TDRE) on a high-speed comparator (SB9696), combining both experimental and simulation methods. Experimental results show that this comparator has two main kinds of transient responses under pulsed gamma-ray environment. First, when the total dose per pulse is less than 54.9 rad(Si), only a short disturbance appears and recovers within several microseconds. Second, when the total dose is beyond 399.6 rad(Si), the comparator is shortly interrupted and then recovers to an under-voltage operation state after several microseconds, and the under-voltage state has a long duration before recovering to a normal working state, which is an uncommon phenomenon that has not been found previously for comparators. A hypothesis is proposed that the short disturbance or interrupt is mainly caused by local photocurrents in the differential structure of the comparator, while the long under-voltage operation state is related to the global photocurrent with a long duration. Lastly, they are successfully verified by SPICE simulations. Simulation results indicate that the short disturbance or interrupt exactly result from local photocurrents in the differential pairs of the comparator’s output module. And, due to the rail-span collapse effect as the global photocurrent flows through power supply lines, the effective supply voltage of the comparator would decrease, thus resulting in a long under-voltage operation state.