A circuit includes a supply circuit having an input and an output. The supply circuit includes: a capacitor having a first terminal and a second terminal, the first terminal of the capacitor coupled to the output of the supply circuit; a switch having a first terminal, a second terminal, and a control terminal, the first terminal of the switch coupled to the input of the supply circuit, the second terminal of the switch coupled to the output of the supply circuit; and a controller coupled to the control terminal of the switch. The controller is configured to: turn on the switch responsive to a first supply voltage level at the input of the supply circuit; and turn off the switch responsive to a second supply voltage level at the input of the supply circuit.