MM54C922,MM54C923,MM74C922,MM74C923 MM54C922 MM74C922 16-Key Encoder MM54C923 MM74C923 20-Key Encoder Literature Number: SNOS345A MM54C922 MM74C922 16-Key Encoder MM54C923 MM74C923 20-Key Encoder July 1993 MM54C922 MM74C922 16-Key Encoder MM54C923 MM74C923 20-Key Encoder
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 kX 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 rollover is provided between any two switches An internal register remembers the last key pressed even after the key is released The TRI-STATE outputs provide for easy expansion and bus operation and are LPTTL compatible Features
Y Y Y Y Y Y Y Y Y Connection Diagrams
Pin Assignment for Dual-In-Line Package Pin Assignment for SOIC bs ol
TL F 6037 14 TL F 60371 Order Number MM74C922 Top View Order Number MM54C922 or MM74C922 O
TRI-STATE is a registered trademark of National Semiconductor Corporation C1995 National Semiconductor Corporation TL F 6037 et
Pin Assignment for DIP and SOIC Package Top View
TL F 6037 2 50 kX 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 TRI-STATE outpust LPTTL compatible Wide supply range Low power consumption e
3V to 15V Top View Order Number MM54C923 or MM74C923
RRD-B30M105 Printed in U S A Absolute Maximum Ratings (Note 1)
If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Voltage at Any Pin Operating Temperature Range MM54C922 MM54C923 MM74C922 MM74C923 VCC b 0 3V to VCC a 0 3V
b 55 C to a 125 C b 40 C to a 85 C Storage Temperature Range Power Dissipation (PD) Dual-In-Line Small Outline Operating VCC Range VCC Lead Temperature (Soldering 10 seconds) b 65 C to a 150 C 700 mW 500 mW 3V to 15V 18V 260 C DC Electrical Characterist …
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