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74AC138 • 74ACT138 1-of-8 Decoder/Demultiplexer
November 1988
Revised July 2003
74AC138 • 74ACT138
1-of-8 Decoder/Demultiplexer
General Description
The AC/ACT138 is a high-speed 1-of-8 decoder/demulti-
plexer. This device is ideally suited for high-speed bipolar
memory chip select address decoding. The multiple input
enables allow parallel expansion to a 1-of-24 decoder
using just three AC/ACT138 devices or a 1-of-32 decoder
using four AC/ACT138 devices and one inverter.
Features
s
I
CC
reduced by 50%
s
Demultiplexing capability
s
Multiple input enable for easy expansion
s
Active LOW mutually exclusive outputs
s
Outputs source/sink 24 mA
s
ACT138 has TTL-compatible inputs
Ordering Code:
Order Number
74AC138SC
74AC138SJ
74AC138MTC
74AC138PC
74ACT138SC
74ACT138SJ
74ACT138PC
Package Number
M16A
M16D
MTC16
N16E
M16A
M16D
N16E
Package Description
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150" Narrow
16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
16-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150" Narrow
16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
Device also available in Tape and Reel. Specify by appending suffix letter “X” to the ordering code.
Connection Diagram
Logic Symbols
IEEE/IEC
Pin Descriptions
Pin Names
A
0
–A
2
E
1
–E
2
E
3
O
0
–O
7
Description
Address Inputs
Enable Inputs
Enable Input
Outputs
FACT is a trademark of Fairchild Semiconductor Corporation.
© 2003 Fairchild Semiconductor Corporation
DS009925
www.fairchildsemi.com
74AC138 • 74ACT138
Truth Table
Inputs
E
1
H
X
X
L
L
L
L
L
L
L
L
H
=
HIGH Voltage Level
Outputs
A
1
X
X
X
L
L
H
H
L
L
H
H
A
2
X
X
X
L
L
L
L
H
H
H
H
O
0
H
H
H
L
H
H
H
H
H
H
H
O
1
H
H
H
H
L
H
H
H
H
H
H
O
2
H
H
H
H
H
L
H
H
H
H
H
O
3
H
H
H
H
H
H
L
H
H
H
H
O
4
H
H
H
H
H
H
H
L
H
H
H
O
5
H
H
H
H
H
H
H
H
L
H
H
O
6
H
H
H
H
H
H
H
H
H
L
H
O
7
H
H
H
H
H
H
H
H
H
H
L
E
2
X
H
X
L
L
L
L
L
L
L
L
E
3
X
X
L
H
H
H
H
H
H
H
H
A
0
X
X
X
L
H
L
H
L
H
L
H
L
=
LOW Voltage Level
X
=
Immaterial
Functional Description
The AC/ACT138 high-speed 1-of-8 decoder/demultiplexer
accepts three binary weighted inputs (A
0
, A
1
, A
2
) and,
when enabled, provides eight mutually exclusive active-
LOW outputs (O
0
–O
7
). The AC/ACT138 features three
Enable inputs, two active-LOW (E
1
, E
2
) and one active-
HIGH (E
3
). All outputs will be HIGH unless E
1
and E
2
are
LOW and E
3
is HIGH. This multiple enable function allows
easy parallel expansion of the device to a 1-of-32 (5 lines
to 32 lines) decoder with just four AC/ACT138 devices and
one inverter (see Figure 1). The AC/ACT138 can be used
as an 8-output demultiplexer by using one of the active
LOW Enable inputs as the data input and the other Enable
inputs as strobes. The Enable inputs which are not used
must be permanently tied to their appropriate active-HIGH
or active-LOW state.
Logic Diagram
Please note that this diagram is provided only for the understanding of logic
operations and should not be used to estimate propagation delays.
FIGURE 1. Expansion to 1-of-32 Decoding
www.fairchildsemi.com
2
74AC138 • 74ACT138
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
CC
)
DC Input Diode Current (I
IK
)
V
I
= −
0.5V
V
I
=
V
CC
+
0.5V
DC Input Voltage (V
I
)
DC Output Diode Current (I
OK
)
V
O
= −
0.5V
V
O
=
V
CC
+
0.5V
DC Output Voltage (V
O
)
DC Output Source
or Sink Current (I
O
)
DC V
CC
or Ground Current
per Output Pin (I
CC
or I
GND
)
Storage Temperature (T
STG
)
Junction Temperature (T
J
)
PDIP
140
°
C
−
0.5V to
+
7.0V
−
20 mA
+
20 mA
−
0.5V to V
CC
+
0.5V
−
20 mA
+
20 mA
−
0.5V to V
CC
+
0.5V
±
50 mA
±
50 mA
−
65
°
C to
+
150
°
C
Recommended Operating
Conditions
Supply Voltage (V
CC
)
AC
ACT
Input Voltage (V
I
)
Output Voltage (V
O
)
Operating Temperature (T
A
)
Minimum Input Edge Rate (
∆
V/
∆
t)
AC Devices
V
IN
from 30% to 70% of V
CC
V
CC
@ 3.3V, 4.5V, 5.5V
Minimum Input Edge Rate (
∆
V/
∆
t)
ACT Devices
V
IN
from 0.8V to 2.0V
V
CC
@ 4.5V, 5.5V
125 mV/ns
Note 1:
Absolute maximum ratings are those values beyond which damage
to the device may occur. The databook specifications should be met, with-
out exception, to ensure that the system design is reliable over its power
supply, temperature, and output/input loading variables. Fairchild does not
recommend operation of FACT circuits outside databook specifications.
2.0V to 6.0V
4.5V to 5.5V
0V to V
CC
0V to V
CC
−
40
°
C to
+
85
°
C
125 mV/ns
DC Electrical Characteristics for AC
Symbol
V
IH
Parameter
Minimum HIGH Level
Input Voltage
V
IL
Maximum LOW Level
Input Voltage
V
OH
Minimum HIGH Level
Output Voltage
V
CC
(V)
3.0
4.5
5.5
3.0
4.5
5.5
3.0
4.5
5.5
3.0
4.5
5.5
V
OL
Maximum LOW Level
Output Voltage
3.0
4.5
5.5
3.0
4.5
5.5
I
IN
(Note 4)
I
OLD
I
OHD
I
CC
(Note 4)
Maximum Input
Leakage Current
Minimum Dynamic
Output Current (Note 3)
Maximum Quiescent
Supply Current
5.5
5.5
5.5
5.5
4.0
0.002
0.001
0.001
T
A
= +25°C
Typ
1.5
2.25
2.75
1.5
2.25
2.75
2.99
4.49
5.49
2.1
3.15
3.85
0.9
1.35
1.65
2.9
4.4
5.4
2.56
3.86
4.86
0.1
0.1
0.1
0.36
0.36
0.36
±0.1
T
A
= −40°C
to
+85°C
Guaranteed Limits
2.1
3.15
3.85
0.9
1.35
1.65
2.9
4.4
5.4
V
IN
=
V
IL
or V
IH
2.46
3.76
4.76
0.1
0.1
0.1
V
IN
=
V
IL
or V
IH
0.44
0.44
0.44
±1.0
75
−75
40.0
µA
mA
mA
µA
V
I
OL
=
12 mA
I
OL
=
24 mA 0
I
OL
=
24 mA (Note 2)
V
I
=
V
CC
, GND
V
OLD
=
1.65V Max
V
OHD
=
3.85V Min
V
IN
=
V
CC
or GND
V
I
OUT
=
50
µA
V
I
OH
= −12
mA
I
OH
= −24
mA
I
OH
= −24
mA (Note 2)
V
I
OUT
= −50 µA
V
V
OUT
=
0.1V
or V
CC
−
0.1V
V
Units
Conditions
V
OUT
=
0.1V
or V
CC
−
0.1V
Note 2:
All outputs loaded; thresholds on input associated with output under test.
Note 3:
Maximum test duration 2.0 ms, one output loaded at a time.
Note 4:
I
IN
and I
CC
@ 3.0V are guaranteed to be less than or equal to the respective limit @ 5.5V V
CC
.
3
www.fairchildsemi.com
74AC138 • 74ACT138
DC Electrical Characteristics for ACT
Symbol
V
IH
V
IL
V
OH
Parameter
Minimum HIGH Level
Input Voltage
Maximum LOW Level
Input Voltage
Minimum HIGH Level
Output Voltage
V
CC
(V)
4.5
5.5
4.5
5.5
4.5
5.5
4.5
5.5
V
OL
Maximum LOW Level
Output Voltage
4.5
5.5
4.5
5.5
I
IN
I
CCT
I
OLD
I
OHD
I
CC
Maximum Input
Leakage Current
Maximum
I
CC
/Input
Minimum Dynamic
Output Current (Note 6)
Maximum Quiescent
Supply Current
5.5
5.5
5.5
5.5
5.5
4.0
0.6
0.001
0.001
T
A
= +25°C
Typ
1.5
1.5
1.5
1.5
4.49
5.49
2.0
2.0
0.8
0.8
4.4
5.4
3.86
4.86
0.1
0.1
0.36
0.36
±0.1
T
A
= −40°C
to
+85°C
Guaranteed Limits
2.0
2.0
0.8
0.8
4.4
5.4
3.76
4.76
0.1
0.1
0.44
0.44
±1.0
1.5
75
−75
40.0
µA
mA
mA
mA
µA
V
Units
V
V
V
Conditions
V
OUT
=
0.1V
or V
CC
−
0.1V
V
OUT
=
0.1V
or V
CC
−
0.1V
I
OUT
= −50 µA
V
IN
=
V
IL
or V
IH
V
I
OH
= −24
mA
I
OH
= −24
mA (Note 5)
I
OUT
=
50
µA
V
IN
=
V
IL
or V
IH
V
I
OL
24 mA
I
OL
.= 24 mA (Note 5)
V
I
=
V
CC
, GND
V
I
=
V
CC
−
2.1V
V
OLD
=
1.65V Max
V
OHD
=
3.85V Min
V
IN
=
V
CC
or GND
Note 5:
All outputs loaded; thresholds on input associated with output under test.
Note 6:
Maximum test duration 2.0 ms, one output loaded at a time.
AC Electrical Characteristics for AC
V
CC
Symbol
Parameter
(V)
(Note 7)
t
PLH
t
PHL
t
PLH
t
PHL
t
PLH
t
PHL
Propagation Delay
A
n
to O
n
Propagation Delay
A
n
to O
n
Propagation Delay
E
1
or E
2
to O
n
Propagation Delay
E
1
or E
2
to O
n
Propagation Delay
E
3
to O
n
Propagation Delay
E
3
to O
n
Note 7:
Voltage Range 3.3 is 3.3V
±
0.3V
Voltage Range 5.0 is 5.0V
±
0.5V
T
A
= +25°C
C
L
=
50 pF
Min
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
Typ
8.5
6.5
8.0
6.0
11.0
8.0
9.5
7.0
11.0
8.0
8.5
6.0
Max
13.0
9.5
12.5
9.0
15.0
11.0
13.5
9.5
15.5
11.0
13.0
8.0
T
A
= −40°C
to
+85°C
C
L
=
50 pF
Min
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.0
Max
15.0
10.5
14.0
10.5
16.0
12.0
15.0
10.5
16.5
12.5
14.0
9.5
ns
ns
ns
ns
ns
ns
Units
3.3
5.0
3.3
5.0
3.3
5.0
3.3
5.0
3.3
5.0
3.3
5.0
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