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National Semiconductor Electronic Components Datasheet


74C922

16/ 20-Key Encoder



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74C922 pdf
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 pull-
up devices which permit switches with up to 50 kX on resist-
ance 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 en-
tered 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 TRI-STATE outputs provide
for easy expansion and bus operation and are LPTTL com-
patible
Features
Y 50 kX maximum switch on resistance
Y On or off chip clock
Y On-chip row pull-up devices
Y 2 key roll-over
Y Keybounce elimination with single capacitor
Y Last key register at outputs
Y TRI-STATE outpust LPTTL compatible
Y Wide supply range
Y Low power consumption
3V to 15V
Connection Diagrams
Pin Assignment for
Dual-In-Line Package
Pin Assignment
for SOIC
Pin Assignment for
DIP and SOIC Package
Top View
TL F 6037–1
Order Number MM54C922 or
MM74C922
TL F 6037 – 14
Top View
Order Number MM74C922
Top View
TL F 6037 – 2
Order Number MM54C923 or
MM74C923
TRI-STATE is a registered trademark of National Semiconductor Corporation
C1995 National Semiconductor Corporation TL F 6037
RRD-B30M105 Printed in U S A



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74C922 pdf
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
VCC b 0 3V to VCC a 0 3V
Operating Temperature Range
MM54C922 MM54C923
b55 C to a125 C
MM74C922 MM74C923
b40 C to a85 C
Storage Temperature Range
Power Dissipation (PD)
Dual-In-Line
Small Outline
Operating VCC Range
VCC
Lead Temperature
(Soldering 10 seconds)
b65 C to a150 C
700 mW
500 mW
3V to 15V
18V
260 C
DC Electrical Characteristics Min Max limits apply across temperature range unless otherwise specified
Symbol
Parameter
Conditions
Min Typ Max Units
CMOS TO CMOS
VTa
VTb
VIN(1)
VIN(0)
Irp
VOUT(1)
VOUT(0)
Ron
ICC
IIN(1)
Positive-Going Threshold Voltage
at Osc and KBM Inputs
Negative-Going Threshold Voltage
at Osc and KBM Inputs
Logical ‘‘1’’ Input Voltage
Except Osc and KBM Inputs
Logical ‘‘0’’ Input Voltage
Except Osc and KBM Inputs
Row Pull-Up Current at Y1 Y2
Y3 Y4 and Y5 Inputs
Logical ‘‘1’’ Output Voltage
Logical ‘‘0’’ Output Voltage
Column ‘‘ON’’ Resistance at
X1 X2 X3 and X4 Outputs
Supply Current
Osc at 0V (one Y low)
Logical ‘‘1’’ Input Current
at Output Enable
VCC e 5V IIN t 0 7 mA
VCC e 10V IIN t 1 4 mA
VCC e 15V IIN t 2 1 mA
VCC e 5V IIN t 0 7 mA
VCC e 10V IIN t 1 4 mA
VCC e 15V IIN t 2 1 mA
VCC e 5V
VCC e 10V
VCC e 15V
VCC e 5V
VCC e 10V
VCC e 15V
VCC e 5V VIN e 0 1 VCC
VCC e 10V
VCC e 15V
VCC e 5V IO e b10 mA
VCC e 10V IO e b10 mA
VCC e 15V IO e b10 mA
VCC e 5V IO e 10 mA
VCC e 10V IO e 10 mA
VCC e 15V IO e 10 mA
VCC e 5V VO e 0 5V
VCC e 10V VO e 1V
VCC e 15V VO e 1 5V
VCC e 5V
VCC e 10V
VCC e 15V
VCC e 15V VIN e 15V
30
60
90
07
14
21
35
80
12 5
45
9
13 5
36
68
10
14
32
5
45
9
13 5
05
1
15
b2
b10
b22
500
300
200
0 55
11
17
0 005
43
86
12 9
20
40
60
15
2
25
b5
b20
b45
05
1
15
1400
700
500
11
19
26
10
V
V
V
V
V
V
V
V
V
V
V
V
mA
mA
mA
V
V
V
V
V
V
X
X
X
mA
mA
mA
mA
IIN(0)
Logical ‘‘0’’ Input Current
at Output Enable
VCC e 15V VIN e 0V
b1 0
b0 005
mA
CMOS LPTTL INTERFACE
VIN(1)
Logical ‘‘1’’ Input Voltage
Except Osc and KBM Inputs
54C VCC e 4 5V
74C VCC e 4 75V
VCC b 1 5
VCC b 1 5
V
V
VIN(0)
Logical ‘‘0’’ Input Voltage
Except Osc and KBM Inputs
54C VCC e 4 5V
74C VCC e 4 75V
08 V
08 V
VOUT(1) Logical ‘‘1’’ Output Voltage
54C VCC e 4 5V
IO e b360 mA
74C VCC e 4 75V
IO e b360 mA
24
24
V
V
VOUT(0) Logical ‘‘0’’ Output Voltage
54C VCC e 4 5V
IO e b360 mA
74C VCC e 4 75V
IO e b360 mA
04 V
04 V
Note 1 ‘‘Absolute Maximum Ratings’’ are those values beyond which the safety of the device cannot be guaranteed Except for ‘‘Operating Temperature Range’’
they are not meant to imply that the devices should be operated at these limits The table of ‘‘Electrical Characteristics’’ provides conditions for actual device
operation
2



Part Number 74C922
Description 16/ 20-Key Encoder
Maker National Semiconductor - National Semiconductor
Total Page 10 Pages
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