WM9714L_06 WOLFSON [Wolfson Microelectronics plc], WM9714L_06 Datasheet - Page 89

• Manufacturer Part Number: WM9714L_06
• Description: AC 97 Audio CODEC
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

Pre-Production
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 34 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 3.0 June 2006
WM9714L
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