Patent ID: 7394172

Claim:
A system comprising: a threshold detector circuit; a first switching circuit for enabling access to a back-up power source, the first switching circuit comprising at least a first transistor; a second switching circuit for enabling access to a primary power source, the second switching circuit comprising at least one transistor; an inverting switch coupled between the first switching circuit and the threshold detector, the inverting switch configured to provide an immediate high output during an on-to-off transition at an input of the inverting switch and a delayed-off output during an off-to-on transition at the input of the inverting switch, the delayed-off output comprising a transition duration from a high to low output responsive to the off-to-on transition that is of a longer duration than a transition duration from a low output to the immediate high output; and an inverter coupled between the inverting switch and the threshold detector circuit, wherein the threshold detector circuit is configured to cause the first switching circuit to enable access to the back-up power source responsive to a voltage provided by the primary power source dropping below a predetermined threshold, wherein the threshold detector circuit is configured to cause the second switching circuit to enable access to the primary power source responsive to a voltage provided by the primary power source rising above the predetermined threshold.