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74C923 - 16-Key Encoder 20-Key Encoder

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.

Features

  • s 50 kΩ maximum switch on resistance s 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: 3V to 15V s Low power consumption Ordering Code: Order Number MM74C922N MM74C922WM MM74C923WM MM74C923N Package Number N18A M20B M20B N20A Package.

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Full PDF Text Transcription

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MM74C922 • MM74C923 16-Key Encoder • 20-Key Encoder October 1987 Revised January 1999 MM74C922 • MM74C923 16-Key Encoder • 20-Key Encoder 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 kΩ 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.
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