TECHNICAL DATA
153
1-of-8 Decoder/Demultiplexer
High-Speed Silicon-Gate CMOS
The IN74AC138 is identical in pinout to the LS/ALS138,
HC/HCT138. The device inputs are compatible with standard CMOS
outputs; with pullup resistors, they are compatible with LS/ALS
outputs.
The IN74AC138 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; 0.1
A @ 25
C
High Noise Immunity Characteristic of CMOS Devices
Outputs Source/Sink 24 mA
IN74AC138
ORDERING INFORMATION
IN74AC138N Plastic
IN74AC138D SOIC
T
A
= -40
to 85
C for all
packages
PIN ASSIGNMENT
LOGIC DIAGRAM
PIN 16 =V
CC
PIN 8 = GND
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
IN74AC138
154
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)
-0.5 to V
CC
+0.5
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 Sink/Source Current, per Pin
50
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
J
Junction Temperature (PDIP)
140
C
T
A
Operating Temperature, All Package Types
-40
+85
C
I
OH
Output Current - High
-24
mA
I
OL
Output Current - Low
24
mA
t
r
, t
f
Input Rise and Fall Time
*
(except Schmitt Inputs)
V
CC
=3.0 V
V
CC
=4.5 V
V
CC
=5.5 V
0
0
0
150
40
25
ns/V
*
V
IN
from 30% to 70% V
CC
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.
IN74AC138
155
DC ELECTRICAL CHARACTERISTICS
(Voltages Referenced to GND)
V
CC
Guaranteed Limits
Symbol
Parameter
Test Conditions
V
25
C
-40
C to
85
C
Unit
V
IH
Minimum High-Level
Input Voltage
V
OUT
=0.1 V or V
CC
-0.1 V
3.0
4.5
5.5
2.1
3.15
3.85
2.1
3.15
3.85
V
V
IL
Maximum Low -
Level Input Voltage
V
OUT
=0.1 V or V
CC
-0.1 V
3.0
4.5
5.5
0.9
1.35
1.65
0.9
1.35
1.65
V
V
OH
Minimum High-Level
Output Voltage
I
OUT
-50
A
3.0
4.5
5.5
2.9
4.4
5.4
2.9
4.4
5.4
V
*
V
IN
=V
IH
or V
IL
I
OH
=-12 mA
I
OH
=-24 mA
I
OH
=-24 mA
3.0
4.5
5.5
2.56
3.86
4.86
2.46
3.76
4.76
V
OL
Maximum Low-Level
Output Voltage
I
OUT
50
A
3.0
4.5
5.5
0.1
0.1
0.1
0.1
0.1
0.1
V
*
V
IN
= V
IH
or V
IL
I
OL
=12 mA
I
OL
=24 mA
I
OL
=24 mA
3.0
4.5
5.5
0.36
0.36
0.36
0.44
0.44
0.44
I
IN
Maximum Input
Leakage Current
V
IN
=V
CC
or GND
5.5
0.1
1.0
A
I
OLD
+Minimum Dynamic
Output Current
V
OLD
=1.65 V Max
5.5
75
mA
I
OHD
+Minimum Dynamic
Output Current
V
OHD
=3.85 V Min
5.5
-75
mA
I
CC
Maximum Quiescent
Supply Current
(per Package)
V
IN
=V
CC
or GND
5.5
8.0
80
A
*
All outputs loaded; thresholds on input associated with output under test.
+Maximum test duration 2.0 ms, one output loaded at a time.
Note: I
IN
and I
CC
@ 3.0 V are guaranteed to be less than or equal to the respective limit @ 5.5 V V
CC
IN74AC138
156
AC ELECTRICAL CHARACTERISTICS
(C
L
=50pF,Input t
r
=t
f
=3.0 ns)
V
CC
*
Guaranteed Limits
Symbol
Parameter
V
25
C
-40
C to
85
C
Unit
Min
Max
Min
Max
t
PLH
Propagation Delay, Input A to Output Y
(Figure 1)
3.3
5.0
1.5
1.5
13.0
9.5
1.5
1.5
15.0
10.5
ns
t
PHL
Propagation Delay, Input A to Output Y
(Figure 1)
3.3
5.0
1.5
1.5
12.5
9.0
1.5
1.5
14.0
10.5
ns
t
PLH
Propagation Delay, CS2 or CS3 to
Output Y (Figure 3)
3.3
5.0
1.5
1.5
15.0
11.0
1.5
1.5
16.0
12.0
ns
t
PHL
Propagation Delay, CS2 or CS3 to
Output Y (Figure 3)
3.3
5.0
1.5
1.5
13.5
9.5
1.5
1.5
15.0
10.5
ns
t
PLH
Propagation Delay, CS1 to Output Y
(Figure 2)
3.3
5.0
1.5
1.5
15.5
11.0
1.5
1.5
16.5
12.5
ns
t
PHL
Propagation Delay, CS1 to Output Y
(Figure 2)
3.3
5.0
1.5
1.5
13.0
8.0
1.5
1.0
14.0
9.5
ns
C
IN
Maximum Input Capacitance
5.0
4.5
4.5
pF
Typical @25
C,V
CC
=5.0 V
C
PD
Power Dissipation Capacitance
60
pF
*
Voltage Range 3.3 V is 3.3 V
0.3 V
Voltage Range 5.0 V is 5.0 V
0.5 V
Figure 1. Switching Waveforms
Figure 2. Switching Waveforms
Figure 3. Switching Waveforms
IN74AC138
157
EXPANDED LOGIC DIAGRAM
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