NTE74C923 Encoders Datasheet

NTE74C923 Datasheet PDF, Equivalent


Part Number

NTE74C923

Description

CMOS Key Encoders

Manufacture

NTE

Total Page 4 Pages
PDF Download
Download NTE74C923 Datasheet PDF


NTE74C923
NTE74C922 & NTE74C923
Integrated Circuit
TTLCMOS Key Encoders
Description:
The NTE74C922 (16Key, 18Lead DIP) and NTE74C923 (20Key, 20Lead DIP) CMOS key en-
coders 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 50kΩ 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 twokey roll
over is provided between any two switches.
An internal register remembers the last key pressed even after the key is released. The 3STATE
outputs provide for easy expansion and bus operation and are LPTTL compatible.
Features:
D 50kΩ Maximum Switch On Resistance
D On or Off Chip Clock
D OnChip Row PullUp Devices
D 2 Key RollOver
D Keybounce Elimination with Single Capacitor
D Last Key Register at Outputs
D 3STATE Output LPTTL Compatible
D Wide Supply range: 3V to 15V
D Low Power Consumption
Absolute Maximum Ratings: (Note 1)
Operating VCC Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3V to 15V
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18V
Voltage at Any Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCC0.3V to VCC+0.3V
Power Dissipation, PD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700mW
Operating Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40° to +85°C
Storage Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65° to +150°C
Lead Temperature (During Soldering, 10 seconds) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +260°C
Note 1. “Absolute Maximum Ratings” are those values beyond which the safety of he device cannot
be guaranteed. Except for “Operating Temperature Range” they are not meant to imply that
the device should be operated at these limits. The table of “Electrical Characteristics”
provides conditions for actual device operation.

NTE74C923
DC Electrical Characteristics: (TA = 40° to +85°C unless otherwise specified)
Parameter
Symbol
Test Conditions
Min Typ
CMOS to CMOS
PositiveGoing Threshold Voltage
at OSC and KBM Inputs
NegativeGoing 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 PullUp 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 X54 Outputs
Supply Current
OSC at 0V, (one Y low)
Logical “1” Input Current at
Output Enable
VT+
VT
VIN(1)
VIN(0)
Irp
VOUT(1)
VOUT(0)
Ron
ICC
IIN(1)
VCC = 5V, IIN 0.7mA
VCC = 10V, IIN 1.4mA
VCC = 15V, IIN 2.1mA
VCC = 5V, IIN 0.7mA
VCC = 10V, IIN 1.4mA
VCC = 15V, IIN 2.1mA
VCC = 5V
VCC = 10V
VCC = 15V
VCC = 5V
VCC = 10V
VCC = 15V
VCC = 5V, VIN = 0.1 VCC
VCC = 10V
VCC = 15V
VCC = 5V, IO = 10μA
VCC = 10V, IO = 10μA
VCC = 15V, IO = 10μA
VCC = 5V, IO = 10μA
VCC = 10V, IO = 10μA
VCC = 15V, IO = 10μA
VCC = 5V, VO = 0.5V
VCC = 10V, VO = 1V
VCC = 15V, VO = 1.5V
VCC = 5V
VCC = 10V
VCC = 15V
VCC = 15V, VIN = 15V
3.0 3.6
6.0 6.8
9.0 10.0
0.7 1.4
1.4 3.2
2.1 5.0
3.5 4.5
8.0 9.0
12.5 13.5
0.5
1.0
1.5
− −2
− −10
− −22
4.5
9.0
13.5
−−
−−
−−
500
300
200
0.55
1.1
1.7
0.005
Logical “0” Input Current at
Output Enable
IIN(0) VCC = 15V, VIN = 0V
1.0 0.005
CMOS/LPTTL Interface
Except OSC and KBM Inputs
Except OSC and KBM Inputs
Logical “1” Output Voltage
Logical “0” Output Voltage
Output Drive (Short Circuit Current)
VIN(1)
VIN(0)
VOUT(1)
VOUT(1)
VCC = 4.75V
VCC = 4.75V
VCC = 4.75V, IO = 360μA,
VCC = 4.75V, IO = 360μA,
VCC1.5
2.4
Output Source Current
(PChannel)
Output Sink Current
(NChannel)
ISOURCE TVAOU=T+=250CV,°C
ISINK
VTAOU=T+=25VCC°CC,
VCC = 5V
VCC =10V
VCC = 5V
VCC =10V
1.75
8
1.75
8
3.3
15
3.6
16
Max
4.3
8.6
12.9
2.0
4.0
6.0
1.5
2.0
2.5
5
20
45
0.5
1.0
1.5
1400
700
500
1.1
1.9
2.6
1.0
0.8
0.4
Unit
V
V
V
V
V
V
V
V
V
V
V
V
μA
μA
μA
V
V
V
V
V
V
Ω
Ω
Ω
mA
mA
mA
μA
μA
V
V
V
V
mA
mA
mA
mA


Features NTE74C922 & NTE74C923 Integrated Circuit TTL− CMOS Key Encoders Description: The NTE74C922 (16−Key, 18−Lead DIP) and NTE74C923 (20−Key, 20−Lead DIP ) CMOS key encoders provide all the nec essary logic to fully encode an array o f SPST switches. The keyboard scan can be implemented by either an external cl ock or external capacitor. These encode rs also have on− chip pull−up devic es which permit switches with up to 50k Ω on resistance to be used. No diodes in the switch array are needed to elimi nate ghost switches. The internal debou nce circuit needs only a single externa l capacitor and can be defeated by omit ting the capacitor. A Data Available ou tput 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 norma l debounce period; this two−key roll− over is provided between any two switche.
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