Experimental Study of Transient Dose Rate Effects of Two Level-Shifting Transceivers and Simulations on Their ESD Circuits

Abstract

This article investigates the transient dose rate effect (TDRE) of two types of level-shifting transceivers. Experimental results show that both transceivers have a high latch-up threshold. One uncommon phenomenon is found that there are photocurrents generated at the input ports for both transceivers when exposed to transient <inline-formula> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> radiation. Moreover, the polarity and amplitude of the photocurrents are related to the input voltage level. A hypothesis is proposed that this uncommon phenomenon is caused by the electrostatic discharge (ESD) circuits at the input ports and then it is successfully verified by TCAD simulations. The simulation results show that the vertical parasitic p-n-p transistor in pMOS of the ESD circuit could turn on under transient <inline-formula> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> radiation, and generate a positive photocurrent when the input port is configured to high-level voltage. On the contrary, when the input port is configured to low-level voltage, its lateral parasitic p-n-p transistor in pMOS could turn on and generate a negative photocurrent. The amplitude of the positive photocurrent is obviously larger than the negative photocurrent due to different gains of the parasitic transistors. Simulation results also show the number of pMOSs in n-well has significant impacts on the amplitude of photocurrents.