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1-of-8 Decoder/Demultiplexer
High-Performance Silicon-Gate CMOS
The IN74HC138A is identical in pinout to the LS/ALS138. The
device inputs are compatible with standard CMOS outputs; with pullup
resistors, they are compatible with LS/ALSTTL outputs.
The IN74HC138A decodes a three-bit Address to one-of-eight
active-low outputs. This device features three Chip Select inputs, two
active-low and one active-high to facilitate the demultiplexing,
cascading, and chip-selecting functions. The demultiplexing function is
accomplished by using the Address inputs to select the desired device
output; one of the Chip Selects is used as a data input while the other
Chip Selects are held in their active states.
•
Outputs Directly Interface to CMOS, NMOS, and TTL
•
Operating Voltage Range: 2.0 to 6.0 V
•
Low Input Current: 1.0 µA
•
High Noise Immunity Characteristic of CMOS Devices
TECHNICAL DATA
IN74HC138A
ORDERING INFORMATION
IN74HC138AN Plastic
IN74HC138AD SOIC
TA = -55° to 125° C for all packages
PIN ASSIGNMENT
LOGIC DIAGRAM
PIN 16 =V
PIN 8 = GND
CC
FUNCTION TABLE
Inputs Outputs
CS1 CS2 CS3 A2 A1 A0 Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7
X X H
X H X
L X X
H L L
H L L
H L L
H L L
H L L
H L L
H L L
H L L
H = high level (ste ady state)
L = low level (steady state)
X = don’t care
X X X
X X X
X X X
L L L
L L H
L H L
L H H
H L L
H L H
H H L
H H H
H H H H H H H H
H H H H H H H H
H H H H H H H H
L H H H H H H H
H L H H H H H H
H H L H H H H H
H H H L H H H H
H H H H L H H H
H H H H H L H H
H H H H H H L H
H H H H H H H L
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IN74HC138A
MAXIMUM RATINGS
*
Symbol Parameter Value Unit
V
CC
V
V
OUT
I
IN
I
OUT
I
CC
P
DC Supply Voltage (Referenced to GND) -0.5 to +7.0 V
DC Input Voltage (Referenced to GND) -1.5 to VCC +1.5 V
IN
DC Output Voltage (Referenced to GND) -0.5 to VCC +0.5 V
DC Input Current, per Pin
DC Output Current, per Pin
DC Supply Current, VCC and GND Pins
Power Dissipation in Still Air, Plastic DIP+
D
SOIC Package+
±
20
±
25
±
50
750
500
Tstg Storage Temperature -65 to +150
T
Lead Temperature, 1 mm from Case for 10 Seconds
L
260
(Plastic DIP or SOIC Package)
*
Maximum Ratings are those values beyond which damage to the device may occur.
Functional operation should be restricted to the Recommended Operating Conditions.
+Derating - Plastic DIP: - 10 mW/°C from 65° to 125°C
SOIC Package: : - 7 mW/°C from 65° to 125°C
mA
mA
mA
mW
°
C
°
C
RECOMMENDED OPERATING CONDITIONS
Symbol Parameter Min Max Unit
V
CC
VIN, V
OUT
T
A
tr, t
f
This device c ontains p rote ction ci rcuitr y to guard a gainst damage d ue to high st atic voltages or electr ic
fields. However, precautions must be taken to avoid applications of any voltage higher than maximum rated
voltages to this high-impedance circuit. For proper operation, V
GND≤(V
IN
Unused inputs must always be tied to an appropriate logic voltage level (e.g., either GND or V
Unused outputs must be left open.
DC Supply Voltage (Referenced to GND) 2.0 6.0 V
DC Input Voltage, Output Voltage (Referenced to GND) 0 V
Operating Temperature, All Package Types -55 +125
Input Rise and Fall Time (Figure 2) VCC =2.0 V
or V
OUT
)≤VCC.
V
V
IN
=4.5 V
CC
=6.0 V
CC
and V
should be constrained to the range
OUT
0
0
0
CC
1000
500
400
V
°
C
ns
CC
).
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IN74HC138A
DC ELECTRICAL CHARACTERISTICS
(Voltages Referenced to GND)
Symbol Parameter Test Conditions V
V
V
V
OH
V
OL
I
IN
Minimum High-Level
IH
Input Voltage
Maximum Low -
IL
Level Input Voltage
Minimum High-Level
Output Voltage
Maximum Low-Level
Output Voltage
Maximum Input
V
=0.1 V or VCC-0.1 V
OUT
≤
I
20 µA
OUT
V
=0.1 V or VCC-0.1 V
OUT
≤
I
20 µA
OUT
VIN=VIH or V
≤
I
OUT
VIN=VIH or V
≤
I
OUT
≤
I
OUT
VIN=VIH or V
≤
I
OUT
VIN=VIH or V
≤
I
OUT
≤
I
OUT
IL
20 µA
IL
4.0 mA
5.2 mA
IL
20 µA
IL
4.0 mA
5.2 mA
VIN=VCC or GND 6.0
Leakage Current
I
CC
Maximum Quiescent
Supply Current
VIN=VCC or GND
=0µA
I
OUT
(per Package)
V
CC
Guaranteed Limit
25 °C
to
≤
85
°
C
≤
125
°
-55°C
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
4.5
6.0
2.0
4.5
6.0
4.5
6.0
1.5
3.15
4.2
0.5
1.35
1.8
1.9
4.4
5.9
3.98
5.48
0.1
0.1
0.1
0.26
0.26
±
0.1
1.5
3.15
4.2
0.5
1.35
1.8
1.9
4.4
5.9
3.84
5.34
0.1
0.1
0.1
0.33
0.33
±
1.0
1.5
3.15
4.2
0.5
1.35
1.8
1.9
4.4
5.9
3.7
5.2
0.1
0.1
0.1
0.4
0.4
±
6.0 4.0 40 160
C
1.0
Unit
V
V
V
V
µ
A
µ
A
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IN74HC138A
AC ELECTRICAL CHARACTERISTICS
(CL=50pF,Input tr=tf=6.0 ns)
Symbol Parameter V
t
PLH
, t
Maximum Propagation Delay, Input A to
PHL
Output Y (Figures 1 and 4)
t
PLH
, t
Maximum Propagation Delay , CS1 to
PHL
Output Y (Figures 2 and 4)
t
PLH
, t
Maximum Propagation Delay , CS2 or CS3 to
PHL
Output Y (Figures 3 and 4)
t
TLH
, t
Maximum Output Transition Time, Any Output
THL
(Figures 2 and 4)
C
IN
Maximum Input Capacitance - 10 10 10 pF
Power Dissipation Capacitance (Per Package)
C
PD
Used to determine the no-load dynamic power
consumption:
P
D=CPDVCC
2
f+ICCV
CC
V
CC
25 °C
to
-55°C
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
135
27
23
110
22
19
120
24
20
75
15
13
Typical @25°C,V
Guaranteed Limit
≤85°
C≤125°C
170
34
29
140
28
24
150
30
26
95
19
16
CC
205
41
35
165
33
28
180
36
31
110
22
19
=5.0 V
55 pF
Unit
ns
ns
ns
ns
144
Figure 1. Switching Waveforms Figure 2. Switching Waveforms
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IN74HC138A
Figure 3. Switching Waveforms Figure 4. Test Circuit
EXPANDED LOGIC DIAGRAM
145
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