Method and Circuit for Maintaining Charge in a Backup Battery

A method eliminates the discharge of the backup battery (42) prior to the primary source of power initially being applied to the device. The method comprises detecting the application of a source of primary power (12) and providing a path by way of a switch (46) in response to receiving the power (14), wherein the path allows the backup battery to power the device. Also, a circuit for maintaining the charge in a backup battery (42) of a device before primary power is applied comprises a sensing circuit (60) for generating an activation signal after initially sensing the application of the primary power to the device, and a switch element (61) coupled the sensing circuit (60) to receive the activation signal. The switch element (61) provides a path for the backup battery (42) to power the device. Accordingly, the method and circuit allow manufacturers of devices incorporating a backup battery (42) to install the backup battery (42) prior to shipping and eliminate the requirement for the purchaser of the device to install the backup battery (42).