Keypad Switches And Scanning - LG MG230 Service Manual

3. TECHNICAL BRIEF

3.3.5 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 21 switches, connected in a matrix of 5 rows by 5 columns
as shown in Figure 3-8, except for the power switch, which is connected independently. Functions, the
row and column lines of the keypad are connected to ports of AD6720. 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 AD6720 to identify
the pressed key.
VBAT
R300
10K
SW300
POWERKEY
R301 680
KEY_ROW0
KEY_ROW1
KEY_ROW2
KEY_ROW3
KEY_ROW4
KEY_COL0
KEY_COL1
KEY_COL2
KEY_COL3
KEY_COL4
LGE Internal Use Only
END
SW301
T
R302 680
R303 680
R316 680
R319 680
R322 680
R329 680
R331 680
R332 680
R333
680
R334 680
Figure 3-8 Keypad Switches and Scanning
- 22 -
VOL_UP VOL_DOWN
1 2 3
SW304 SW305 SW306
SW309 SW310 SW311
4 5 6
SW314 SW315 SW316
7 8 9
SW319 SW320 SW321
* 0 #
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
CLR FAV
SW302 SW303
LEFT
SW307 SW308 MENU
SW312 SW313
UP
SEL
SW317 SW318
RIGHT
SEND
SW322 SW323
DOWN
CONF