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3. TECHNICAL BRIEF
(2) Key Backlight Illumination
There are 6 blue LEDs for key backlight illumination which are driven by KEY_BACKLIGHT
signal from AD6525.
VBAT
$V
$V
$V
$V
$V
$V
3.11 Microphone
The microphone is placed to the front cover and is connected to main PCB. The audio
signal is passed to VINNORP and VINNORN pins of AD6521. The voltage supply 2V55_VAN
is output from ADP3522, and is a bias voltage for the VINNORP.
The VINNORP and VINNORN signals are A/D converted by the Voiceband ADC part of
AD6521. The digitized speech is then passed to the DSP section of AD6525 for
processing (coding, interleaving etc).
VINNORP
VINNORN
C319
C320
C321
C322
27p
27p
27p
27p
$V
$V
$V
$V
$V
$V
$V
$V
$V
$V
Figure 3-16 Circuit Diagram of key backlight illumination
C216
C250
39p
10u
(1608)
R211
R240
0
100
R214
100
Figure 3-17 Circuit Diagram of Microphone
KEY BACKLIGHT
C323
C324
27p
27p
$V
$V
$V
$V
$V
$V
MAX4599EXT-T
$V
R316
$V
RPWRON
2V55_VAN
C217
10u
C219
39p
CLOSE TO MIC
- 30 -
VCHARGE
VBAT
$V
$V
U302
NO
R312
6
$V
COM
0
NC
4
C318
0.1u
$V
$V
0
MIC200
1
2
OB4-15L42-C33L
KEY_BACKLIGHT
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