Patent ID: 8264801

Claim:
An arrangement for selectively coupling one of a primary power supply and a backup power supply to an output for operating a circuit, the arrangement comprising: a primary switch to couple the primary power supply to the output; a backup switch to couple the backup power supply to the output; and a controller circuit to control the operation of the switches for selectively coupling the primary and backup supplies to the output as a function of a voltage level of the primary and backup power supplies and a predetermined backup-mode threshold voltage, the controller circuit configured and arranged to compare a level of the primary power supply to the predetermined backup-mode threshold voltage and to the backup power supply and including a levelshifter circuit to supply a voltage input to the primary and backup switches for controlling the switches in on and off states in response to a high voltage input, and a high voltage supply circuit to selectively supply the high voltage input using the higher of the primary and backup power supply voltages.