General Description

These 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 pullup devices which permit switches with up to 50 kXon resistance to be used. No diodes in the switch array are needed to eliminate ghost switches.

Features

50 kXmaximum 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

TRI-STATE outpust LPTTL compatible

Wide supply range 3V to 15V

Low power consumption