- 36 -
LGE Internal Use Only
Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL BRIEF
LGE Internal Use Only
3.3.2 Analog Audio Input
The AD6725-ATLAS3HLITE provides two analog input channels, AIN1 and AIN2, that may be used for both
microphone and line inputs. The AIN1 and AIN2 channels are identical. One of the
two channels is typically used with microphone built into a handset. The other channel is
typically used with an external microphone or external line input.
Figure 3-2-4 AD6725-ATLAS3HLITE Audio Input Block Diagram
Analog Input AIN1, AIN2 and VMIC configurations can be chosen by setting bits AudIS[3:0] in the
AudControl2 register (0x1E ). Additional gain of 9dB can be inserted into Analog Audio Input signal chain
by setting AudPreampGainSel bit high in the AudControl3 register (0x32 ).
Microphone Interface
The microphone pre-amplifier and associated integrated resistors support electret microphones. An
internal (Configuration 11) or external (Configuration 01 or 10) load resistor converts the current input of
the microphone to a voltage signal which is amplified using a low-noise pre-amplifier. The Microphone
signal path also includes an additional programmable gain of +9 dB gain directly after the pre-amplifier.
Different microphones require different DC bias currents for optimum sensitivity.