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LGE Internal Use Only
Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL BRIEF
The key switches are metal domes, which make contact between two concentric pads on the
keypad layer of the PCB when pressed. There are 22 switches (Normal Key 22EA), connected in a matrix of 5
rows by 5 columns, as shown in Figure 3-8, except for the power switch (END), which is connected
independently. Functions, the row and column lines of the keypad are connected to ports of AD6726. 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 AD6726 to identify the pressed key.
Figure 3.8 Keypad Switches and Scanning
3.8 Keypad Switches and Scanning
4
5
6
UP
CONF
CLR
1
LEFT
MENU
PWR
9
7
SEL
0
8
*
DOWN
#
RIGHT
SEND
2
3
VA201
EVL14S02200
SW207
680
R215
DOWN
C246
DNI
END
680
R217
SW206
LEFT
R213
680
SW209
UP
C248
DNI
680
R204
SW203
SEL
DNI
C239
DNI
C247
STAR
680
R219
SW200
SW201
SW204
SW205
DNI
C249
C238
DNI
DNI
C242
SHARP
VA200
EVL14S02200
CONF
C241
DNI
R216
680
SW202
SEND
R218
680
SW208
MENU
R206
680
CLR
680
R211
R209
680
RIGHT
680
R210
POWERKEY
KEY_COL4
KEY_COL3
KEY_COL2
KEY_COL1
KEY_COL0
KEY_ROW0
KEY_ROW1
KEY_ROW2
KEY_ROW3
KEY_ROW4