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Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
3. TECHNICAL BRIEF
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
Audio Accessory Detection
The AD6725 provides for detection of audio headset accessory insertion, extraction, and hookswitch
events. The detector circuit is designed to operate with minimum power in standby mode. There are
two pins dedicated to the accessory detector. AccDet is intended to interface to the external
microphone and monitor its bias voltage. The ACCDET terminal is used to sense hookswitch events
while a headset accessory is inserted. The JackSense terminal is interfaced to the switch pin of the Jack
socket or a Jack Sense terminal on a handset system connector.
Use of the AccDet Terminal for Hookswitch Event Detection
The AccDet terminal may be connected directly to the Ain2P pin in the case of a DC coupling of the
accessory microphone. If the accessory microphone is connected via a capacitor then the AccDet pin
may be connected to the microphone side of the coupling capacitor. The AccDet terminal is used to
detect hookswitch events. Hookswitch events cause the system to answer an incoming phone call or
hang up on an active phone call.
The detector circuit is in operation only if an accessory is inserted. It monitors the voltage at the AccDet
terminal using a comparator as shown Figure below.
Associated logic then provides the AudAccInt interrupt and updates the contents of the Detector
Control register as follows on each comparator transition
Figure 3-13-5 Audio Accessory Detection Block Diagram