Low-power on-chip headset switch detection

A circuit comprising:

• a terminal;
• a voltage regulator connected to the terminal that is disabled in a first operating mode and that is enabled in a second operating mode, wherein when the voltage regulator is enabled it supplies a regulated voltage onto the terminal;
• and
• a low-power switch detect circuit comprising a current mirror, a resistor, and an inverter, wherein the current mirror comprises a first leg and a second leg, wherein the first leg is connected to the terminal, wherein in the first operating mode the low-power switch detect circuit supplies a current through the first leg that flows out of the circuit through the terminal and supplies a mirrored current through the second leg to the resistor and the inverter,
• wherein the low-power switch detect circuit is configured to:
• detect whether the mirrored current through the second leg exceeds a threshold current;
• output a first digital logic value if the low-power switch detect circuit detects that the mirrored current through the second leg exceeds the threshold current;
• and
• output a second digital logic value if the low-power switch detect circuit detects that the mirrored current through the second leg does not exceed the threshold current wherein when the current flows out of the circuit in the first operating mode there is an unregulated voltage on the terminal.

A circuit adapted for coupling to a microphone assembly, the microphone assembly including a microphone, a manually-operable switch, and a conductor, the circuit comprising:

• a terminal that is detachably couple to the conductor of the microphone assembly;
• means for supplying a regulated voltage onto the terminal in a second operating mode and for detecting a condition in the second operating mode when the switch of the microphone assembly is closed;
• means for supplying a current onto the terminal in a first operating mode such that a voltage on the terminal is an unregulated voltage, and for detecting a condition in the first operating mode when the switch on the microphone assembly is closed;
• and
• wherein the means for supplying the current onto the terminal comprises a current mirror, an resistor, and an inverter, wherein the current mirror comprises a first leg and a second leg, wherein the current minor supplies the current onto the terminal through the first leg, and wherein the current mirror supplies a mirrored current onto the second leg and to the resistor and the inverter for detecting the condition.