Product Summary

The 74C923 is a key encoder providing 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. The 74C923 has on-chip pull-up devices which permits switches with up to 50 kΩ on resistance to be used. No diodes in the switch array are needed to eliminate ghost switches. The internal debounce circuit of the 74C923 needs only a single external capacitor and can be defeated by omitting the capacitor.

Parametrics

74C923 absolute maximum ratings: (1)Voltage at Any Pin VCC: -0.3V to VCC + 0.3V; (2)Operating Temperature Range: -40 to +85℃; (3)Storage Temperature Range: -65 to +150℃; (4)Power Dissipation, PD: 700 mW; (5)Operating VCC Range: 3V to 15V; (6)Lead Temperature (Soldering, 10 seconds): 260℃.

Features

74C923 features: (1)50 kΩ maximum switch on resistance; (2)On or off chip clock; (3)On-chip row pull-up devices; (4)2 key roll-over; (5)Keybounce elimination with single capacitor; (6)Last key register at outputs; (7)3-STATE output LPTTL compatible; (8)Wide supply range: 3V to 15V; (9)Low power consumption.

Diagrams

74C923 block diagram