CM2500-05 Datasheet, PDF (4/5 Pages) California Micro Devices Corp – CMOS Multiplexer for Keypad Switches

Applications Information
CM2500-05
VCC
Col1
Col2
Col3
Col4
Row1
Row2
Row3
Row4
SW4
SW3
SW2
SW1
SW8
SW7
SW6
SW5
SW12
SW11
SW10
SW9
SW16
SW15
SW14
SW13
CM2500-05
OUTA
OUT1
OUT2
OUT3
OUT4
OUT5
OUTB
VCC
IN1
IN2
IN3
IN4
IN5
GND
SW17
SW18
SW19
SW20
SW21
Figure 1. Typical Application for Extended 4X4 Keyboard
The CM2500-05 can be used with just about any key-
pad configuration. The diagram below gives an exam-
ple of an interface for a 4 column x 4 row
implementation. The outputs of the CM2500-05 have
been designed to interface with nearly any type of key-
board setup provided the same methodology is used.
Basically if any one of the switches 17 to 21 are closed,
it will pull down 2 row lines rather than 1. All outputs on
the CM2500-05 are open drain.
It follows in the above implementation that:
• If SW17 is closed, row 1 and 2 are pulled low.
• If SW18 is closed, row 1 and 3 are pulled low.
• If SW19 is closed, row 1 and 4 are pulled low.
• If SW20 is closed, row 2 and 3 are pulled low.
• If SW21 is closed, row 2 and 4 are pulled low.
• If SW17-SW21 are not closed, the standard scan
routine is in effect (i.e., one row is pulled low)
In larger keypad implementations, multiple CM2500-05
can be used to yield more switches.
© 2004 California Micro Devices Corp. All rights reserved.
4 430 N. McCarthy Blvd., Milpitas, CA 95035-5112 ● Tel: [phone] ● Fax: [phone] ● www.calmicro.com 09/21/04