wm9714l Wolfson Microelectronics plc, wm9714l Datasheet - Page 114

• Manufacturer Part Number: wm9714l
• Description: Ac?97 Audio Codec
• Manufacturer: Wolfson Microelectronics plc

WM9714L
HOOKSWITCH DETECTION
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Alternatively a headphone socket with a switch that opens on insertion can be used. For this mode
of operation the GPIO input must be inverted.
The circuit diagram below shows how to detect when the “hookswitch” of a phone headset is pressed
(pressing the hookswitch is equivalent to lifting the receiver in a stationary telephone).
Figure 36 Hookswitch Detection Circuit
The circuit uses a GPIO pin as a sense input. The impedance of the microphone and the resistor in
the MICBIAS path must be such that the potential at the GPIO pin is above 0.7×DBVDD when the
hookswitch is open, and below 0.3×DBVDD when it is closed.
PP, Rev 3.2, October 2008
Pre-Production
114