Only For Training And Service Purposes - LG KG290 Service Manual

5. Microphone
The main microphone is soldered to the main PCB. The audio signal is passed to AIN1P(#P16),
AIN1N(#R16), AIN2P(#P15) and AIN2N(#R15) pins of AD6721.
The voltage supply 2V5_VMIC is output from AD6721. The voltage supply 2V5_JACK is output from
BH25FB1WHFV (Low Drop Output). The VIN1 and VIN2 signals are A/D converted by the Voiceband
ADC part of AD6721. The digitized speech is passed to the DSP section for processing(coding,
interleaving etc.) The Microphone interface is shown in Figure 4.
MIC_P
MIC_N
Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

2V5_VMIC
R221
1K
R227
2.2K
R231 100ohm
C222
39p
C228 0.1u
R232 100ohm
R234
2.2K
R228
AUXIP
C220
AUXIN
C224 C225
27p 27p
Figure 5. Microphone(main & aux)
3. TECHNICAL BRIEF
C219 C215
10u
39p
C223
39p
2V8_VMEM
R225
3K
0.1u R229
0.1u
C226
10u
- 51 -
OB4-15L42-C33L
2
1
MIC200
1.5K
LGE Internal Use Only