74C922-SO Datasheet, PDF (1/5 Pages) ABCircuits – Keyboard / Keypad Encoder for up to 16 switches

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74C922-SO IC
Keyboard / Keypad Encoder for up to 16 switches
MM74C922 Replacement IC
General Description
The 74C922-SO is designed as a replacement chip for the obsolete MM74C922 surface mount
part. The 74C922-SO contains all the logic necessary to encode a SPST keyboard switch array
up to 4 by 4 in size and provide a 4 bit parallel output and a data available signal. The data
available signal goes high when a key is pressed, and goes low before another key output is
generated. The data output pins keep their state even after the key is released. The array can
be a 4 x 4 array, but smaller arrays such as a 3 x 4 array or any smaller size can be used. The
74C922-SO handles debouncing of the keys as well. No external capacitors are required for
timing; all timing is internally generated. No external diodes are required in the array to prevent
key ghosting in a two key rollover situation. A .1 uF bypass capacitor is suggested across the
VDD and VSS pins. The part uses the standard 20 pin .3 inch width SOIC package.
Features
• Replacement Chip for MM74C922
• Fully encodes a key switch array. (up to 4 x 4)
• No external parts required.
• Low power consumption 1.5 mA typical.
• Supply voltage 2.4 to 5.25 volts.
• Last key pressed retained on data outputs.
• All timing internally generated.
• 2 Key rollover.
• On chip row input resistors.
• Internal key bounce elimination.
• TTL and CMOS compatible outputs.
• Part is in full production.
• SOIC 20 Pin Package.
• ROHS Compliant
• Low EMI
Part Number 74C922-SO
December 2012 Page 1 of 5