General Description

The MM74C922 and MM74C923 CMOS key encoders provide all the necessary logic to fully encode an array of SPST switches. The keyboard scan can be implemented by either an external clock or external capacitor. These encoders also have on-chip pull-up devices which permit switches with up to 50 kΩon resistance to be used.

Features

■ 50 kΩmaximum switch on resistance

■ On or off chip clock

■ On-chip row pull-up devices

■ 2 key roll-over

■ Keybounce elimination with single capacitor

■ Last key register at outputs

■ 3-STATE output LPTTL compatible

■ Wide supply range: 3V to 15V

■ Low power consumption