Patent ID: 7915920

Claim:
In an apparatus comprising a circuit coupled to receive a first input signal from a level shifter, wherein the level shifter and the circuit are supplied by a first supply voltage during use, and wherein the level shifter is configured to generate the first input signal responsive to a second input signal to the level shifter, wherein the second input signal is generated by circuitry supplied with a second supply voltage during use, a method comprising: detecting that the second supply voltage is to be powered down; asserting a power control signal to the level shifter responsive to the detecting; generating a predetermined level on the first input signal responsive to the asserting and independent of the second input signal, the generating performed by the level shifter; and delaying a period of time after the asserting of the power control signal before powering down the second supply voltage to a ground reference, wherein the period of time is at least sufficient for the level shifter to stabilize at the predetermined level.