Only For Training And Service Purposes - LG GM210 Service Manual

3. TECHNICAL BRIEF
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.
Audio ADC and PGA
The Audio ADC is a high-order single-bit sigma-delta ADC that includes a switched- capacitor PGA at the
input.
Digital Filters
The AD6725 Audio Section provides two digital filters. The voiceband filter is used for applications with a 8
kHz digital sample rate. The high-quality audio filter is used for applications with higher digital sample
rates.
LGE Internal Use Only
LGE Internal Use Only
Copyright © 2008 LG Electronics. Inc. All right reserved.

Only for training and service purposes

- 50 - Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes