Keypad Switches And Scanning - LG G5300 Service Manual

3.12 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 19 switches (S301-S325, not used S303~S309),
connected in a matrix of 5 rows by 5 columns, as shown in Figure, except for the power switch
(S310), which is connected independently. Functions, the row and column lines of the keypad are
connected to ports of AD6522. 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 AD6522 to identify the pressed key.
POWERKEY
KEYROW0
KEYROW1
KEYROW2
KEYROW3
KEYROW4
KEYCOL0
KEYCOL1
KEYCOL2
KEYCOL3
KEYCOL4
KB101
ON/OFF
KB103 KB104
1
SP102
KB108 KB109
4
SP103
KB112 KB113
7
SP104
KB116 KB117
*
SP105
SP106
SP110
Figure 3-29. Keypad Switches and Scanning.
- 43 -
KB102
C
KB105 KB106
2 3
SOFT2
KB110 KB111
5 6
SEND
KB114 KB115
8 9
SOFT1
KB118
0 #
SP107 SP108
3. TECHNICAL BRIEF
KB107
UP
KB119
DOWN
SP109