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3. TECHNICAL BRIEF
LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3.8 Keypad Switches and Scanning
The key switches are metal domes, which make contact between two concentric pads on the keypad
layer of the PCB when pressed. There are 27 switches (Normal Key 23EA, Volume up down and
camera side key, PWR down side key), connected in a matrix of 6 rows by 5 columns, as shown in
Figure 3-11, except for the power switch (END), which is connected independently. Functions, the row
and column lines of the keypad are connected to ports of AD6721. The columns are outputs, while the
rows are inputs and have pull-up resistors built in. When a key is pressed, the corresponding row and
column are connected together, causing the row input to go low and generate an interrupt. The
columns/rows are then scanned by AD6721 to identify the pressed key.
MENU
1
T
END
VOL_UP
UP
VOL_DOWN
Side Key
CONF
9
8
2
LEFT
0
CLR
RIGHT
FAV
*
4
6
7
5
#
3
SEND
CAMERA
SEL
DOWN
100K
R337
SW307
UP
680
R321
3
4
5
680
R336
CN300
1
2
R325
680
VA301
ESD9X5.0ST5G
INSTPAR
FAV
680
R338
LEFT
SW304
SW301
INSTPAR
ESD9X5.0ST5G
VA300
680
R302
R342
680
SW309
SW308
RIGHT
SW305
SEL
DOWN
SW302
VA307
ESD9X5.0ST5G
680
R333
680
VA303
ICVS0514X350FR
R328
R313
100ohm
SW303
END
680
R341
680
R343
CLR
*
R312
SW300
100ohm
SEND
CONF
ICVS0514X350FR
VA302
R340
680
R311
100ohm
2V8_VEXT
SW306
T
680
R339
MENU
SHARP
KEY_ROW5
KEY_COL4
KEY_COL3
KEY_COL2
KEY_ROW1
KEY_ROW2
KEY_ROW4
KEY_COL0
KEY_ROW0
POWERKEY
KEY_ROW3
KEY_COL1
Figure 3.8 Keypad Switches and Scanning
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