Patent ID: 8077878

Claim:
A method, comprising: (a) in a second operating mode of a circuit, using a voltage regulator to supply a regulated voltage onto a microphone bias (MIC BIAS) terminal of the circuit; (b) in a first operating mode of the circuit, maintaining the voltage regulator in a disabled state and supplying, using a first current mirror having a first leg coupled to the MIC BIAS terminal and a second leg, a first current in a current path out of the circuit through the MIC BIAS terminal; and (c) in the first operating mode of the circuit, mirroring the first current using the current mirror to generate a first mirrored current at the second leg, receiving, by a resistor and an inverter, the first mirrored current, and generating a digital signal based on a level of the first mirrored current, wherein the digital signal has a first digital value if the first mirrored current exceeds a threshold current, and wherein the digital signal has a second digital value if the first mirrored current does not exceed the threshold current.