Booster circuit with capacitor protection circuitry

Abstract

Booster circuitry is provided that contains capacitor protection circuitry. The booster circuitry receives a digital input signal on an input line and provides a corresponding boosted digital output signal on an output line. The digital input signal may be received from an oscillator. The digital output signal may be a clock that is applied to a charge pump on a programmable logic device integrated circuit. The booster circuitry contains a metal-oxide-semiconductor capacitor. The capacitor protection circuitry ensures that the voltage across the capacitor in the booster circuit remains above a desired minimum voltage and below a desired maximum voltage during operation. The capacitor protection circuitry includes a control circuit that monitors the capacitor voltage when the booster circuit is operated while the oscillator is off and transistor-based circuitry that discharges one of the capacitor's terminals to a predetermined level when the booster circuit is operated while the oscillator is on.