TECHNICAL DATA
141
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
A
High Noise Immunity Characteristic of CMOS Devices
IN74HC138A
ORDERING INFORMATION
IN74HC138AN Plastic
IN74HC138AD SOIC
T
A
= -55
to 125
C for all packages
PIN ASSIGNMENT
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
X X X
X X X
X X X
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 L
H L L
H L L
H L L
L L L
L L H
L H L
L 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 L L
H L L
H L L
H L L
H L L
H L H
H H L
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 = high level (steady state)
L = low level (steady state)
X = don't care
LOGIC DIAGRAM
PIN 16 =V
CC
PIN 8 = GND
IN74HC138A
142
MAXIMUM RATINGS
*
Symbol
Parameter
Value
Unit
V
CC
DC Supply Voltage (Referenced to GND)
-0.5 to +7.0
V
V
IN
DC Input Voltage (Referenced to GND)
-1.5 to V
CC
+1.5
V
V
OUT
DC Output Voltage (Referenced to GND)
-0.5 to V
CC
+0.5
V
I
IN
DC Input Current, per Pin
20
mA
I
OUT
DC Output Current, per Pin
25
mA
I
CC
DC Supply Current, V
CC
and GND Pins
50
mA
P
D
Power Dissipation in Still Air, Plastic DIP+
SOIC Package+
750
500
mW
Tstg
Storage Temperature
-65 to +150
C
T
L
Lead Temperature, 1 mm from Case for 10 Seconds
(Plastic DIP or SOIC Package)
260
C
*
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
RECOMMENDED OPERATING CONDITIONS
Symbol
Parameter
Min
Max
Unit
V
CC
DC Supply Voltage (Referenced to GND)
2.0
6.0
V
V
IN
, V
OUT
DC Input Voltage, Output Voltage (Referenced to GND)
0
V
CC
V
T
A
Operating Temperature, All Package Types
-55
+125
C
t
r
, t
f
Input Rise and Fall Time (Figure 2)
V
CC
=2.0 V
V
CC
=4.5 V
V
CC
=6.0 V
0
0
0
1000
500
400
ns
This device contains protection circuitry to guard against damage due to high static voltages or electric
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
IN
and V
OUT
should be constrained to the range
GND
(V
IN
or V
OUT
)
V
CC
.
Unused inputs must always be tied to an appropriate logic voltage level (e.g., either GND or V
CC
).
Unused outputs must be left open.
IN74HC138A
143
DC ELECTRICAL CHARACTERISTICS
(Voltages Referenced to GND)
V
CC
Guaranteed Limit
Symbol
Parameter
Test Conditions
V
25
C
to
-55
C
85
C
125
C
Unit
V
IH
Minimum High-Level
Input Voltage
V
OUT
=0.1 V or V
CC
-0.1 V
I
OUT
20
A
2.0
4.5
6.0
1.5
3.15
4.2
1.5
3.15
4.2
1.5
3.15
4.2
V
V
IL
Maximum Low -
Level Input Voltage
V
OUT
=0.1 V or V
CC
-0.1 V
I
OUT
20
A
2.0
4.5
6.0
0.5
1.35
1.8
0.5
1.35
1.8
0.5
1.35
1.8
V
V
OH
Minimum High-Level
Output Voltage
V
IN
=V
IH
or V
IL
I
OUT
20
A
2.0
4.5
6.0
1.9
4.4
5.9
1.9
4.4
5.9
1.9
4.4
5.9
V
V
IN
=V
IH
or V
IL
I
OUT
4.0 mA
I
OUT
5.2 mA
4.5
6.0
3.98
5.48
3.84
5.34
3.7
5.2
V
OL
Maximum Low-Level
Output Voltage
V
IN
=V
IH
or V
IL
I
OUT
20
A
2.0
4.5
6.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
V
V
IN
=V
IH
or V
IL
I
OUT
4.0 mA
I
OUT
5.2 mA
4.5
6.0
0.26
0.26
0.33
0.33
0.4
0.4
I
IN
Maximum Input
Leakage Current
V
IN
=V
CC
or GND
6.0
0.1
1.0
1.0
A
I
CC
Maximum Quiescent
Supply Current
(per Package)
V
IN
=V
CC
or GND
I
OUT
=0
A
6.0
4.0
40
160
A
IN74HC138A
144
AC ELECTRICAL CHARACTERISTICS
(C
L
=50pF,Input t
r
=t
f
=6.0 ns)
V
CC
Guaranteed Limit
Symbol
Parameter
V
25
C
to
-55
C
85
C
125
C
Unit
t
PLH
, t
PHL
Maximum Propagation Delay, Input A to
Output Y (Figures 1 and 4)
2.0
4.5
6.0
135
27
23
170
34
29
205
41
35
ns
t
PLH
, t
PHL
Maximum Propagation Delay , CS1 to
Output Y (Figures 2 and 4)
2.0
4.5
6.0
110
22
19
140
28
24
165
33
28
ns
t
PLH
, t
PHL
Maximum Propagation Delay , CS2 or CS3 to
Output Y (Figures 3 and 4)
2.0
4.5
6.0
120
24
20
150
30
26
180
36
31
ns
t
TLH
, t
THL
Maximum Output Transition Time, Any Output
(Figures 2 and 4)
2.0
4.5
6.0
75
15
13
95
19
16
110
22
19
ns
C
IN
Maximum Input Capacitance
-
10
10
10
pF
Power Dissipation Capacitance (Per Package)
Typical @25
C,V
CC
=5.0 V
C
PD
Used to determine the no-load dynamic power
consumption:
P
D
=C
PD
V
CC
2
f+I
CC
V
CC
55
pF
Figure 1. Switching Waveforms Figure 2. Switching Waveforms
IN74HC138A
145
Figure 3. Switching Waveforms
Figure 4. Test Circuit
EXPANDED LOGIC DIAGRAM
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