MM74C922 74HC922N Multiplexer IC

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 k on resistance to be used. No diodes in the switch array are needed to eliminate ghost switches. The internal debounce circuit needs only a single external capacitor and can be defeated by omitting the capacitor. A Data Available output goes to a high level when a valid keyboard entry has been made. The Data Available output returns to a low level when the entered key is released, even if another key is depressed. The Data Available will return high to indicate acceptance of the new key after a normal debounce period; this two-key roll-over is provided between any two switches. An internal register remembers the last key pressed even after the key is released. The 3-STATE outputs provide for easy expansion and bus operation and are LPTTL compatible.

50 k maximum switch on resistance On or off chip clock s On-chip row pull-up devices s 2 key roll-over s Keybounce elimination with single capacitor s Last key register at outputs s 3-STATE output LPTTL compatible s Wide supply range: 15V s Low power consumption

Order Number MM74C923WM MM74C923N Package Number M20B N20A Package Description 20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide 18-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide 20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide 20-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide

Device also available in Tape and Reel. Specify by appending suffix letter "X" to the ordering code.

(Pins 0 through 11) Switch Position (Pins 12 through 19) Switch 12 Position

Features
■ 50 kΩ maximum 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

Package Includes

1pc x MM74C922 74HC922N  Multiplexer IC