Texas Instruments Corporation

Ball Fan

Jie Feng

Danyang Zhu

Xiaonan Wang

Christopher Michael Graves

Wenpang David Wang

An audio accessory key detection system () includes a host circuit (-) coupled to communicate via a microphone line () with an accessory circuit (-) in either a MSFT mode or a digital communication mode. Depletion mode transistors (-) in the accessory circuit are coupled between keys (-) of the accessory circuit, respectively. The depletion mode transistors are allowed to remain conductive for MSFT mode operation. For digital communications mode operation, the host circuit sends a command via the microphone line to a key detector and controller circuit (A) in the accessory circuit. In response, a voltage is generated to turn the depletion mode transistors off so as to allow digital communications mode operation between the accessory circuit and the host circuit.

Operating a headset that includes microphone line and pushbutton keys

A lever shifter includes an output driver and a high-side gate driver. The high-side gate driver is configured to drive the high-side output transistor, and is coupled to an on pulse signal line that conducts an on pulse, and is coupled to an off pulse signal line that conducts an off pulse. The high-side gate driver includes a blocking circuit configured to enable generation of a drive signal to the high-side output transistor based on a voltage of a first of the on or off pulse signal line being greater than a first predetermined amount and a voltage of a second of the on or off signal line being less than a second predetermined amount.

High voltage level shifter with short propagation delay

Initial command to switch transistors disconnecting keys from microphone line

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Tianjin, China

Ball Fan