Total ionizing dose effects in CMOS low-dropout regulators: Experiments and bias-dependent simulations

This paper investigates the total ionizing dose (TID) response of commercial low-dropout regulators (LDOs) through experiments and simulations. Co-60 γ irradiation tests were performed on RT9013 and XC6219 LDOs at a dose rate of 50 rad(Si)/s. The results show that the output voltage decreases with increasing dose, while electrical bias and load condition accelerate degradation and reduce the failure threshold. To explain these behaviors, a bias-dependent TID simulation method is developed by combining TCAD, SPICE, and Python-based automatic netlist generation. The method incorporates the actual operating bias of internal transistors and dimensional correction. The error amplifier (EA), bandgap reference (BGR), pass transistor, and complete LDO are analyzed separately. The results show that EA degradation causes abrupt output collapse, whereas BGR degradation mainly leads to gradual reference-voltage reduction. The PMOS pass transistor exhibits weak TID sensitivity within the investigated dose range. A dual sensitivity analysis further identifies the dominant transistor-level contributors in the EA and BGR. These results provide an effective approach for understanding and predicting TID-induced degradation in CMOS LDO circuits.