Modeling Total-Dose Effects for a Low-Dropout Voltage Regulator

Total ionizing dose effects in a low-dropout voltage regulator are explained based on experimental data and circuit simulations. Transistor gain degradation is shown to be the dominant cause of the circuit degradation at lower dose rates. In addition, collector-to-emitter leakage current in one of the NPN transistors of the bandgap reference part of the circuit is responsible for increasing the postirradiation output voltage at high dose rates. Parametric changes in the bandgap, differential amplifier, and output pass transistor circuit blocks are identified that are responsible for various aspects of the observed circuit degradation. The different annealing characteristics of oxide-trap and interface-trap charge are responsible for the complex postirradiation recovery of the output voltage.