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74F138 1-of-8 Decoder/Demultiplexer
April 1988
Revised September 2000
74F138
1-of-8 Decoder/Demultiplexer
General Description
The F138 is a high-speed 1-of-8 decoder/demultiplexer.
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 F138 devices or a 1-of-32 decoder using four F138
devices and one inverter.
Features
s
Demultiplexing capability
s
Multiple input enable for easy expansion
s
Active LOW mutually exclusive outputs
Ordering Code:
Order Number
74F138SC
74F138SJ
74F138PC
Package Number
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 Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Logic Symbols
Connection Diagram
IEEE/IEC
© 2000 Fairchild Semiconductor Corporation
DS009478
www.fairchildsemi.com
74F138
Unit Loading/Fan Out
U.L.
Pin Names
A
0
–A
2
E
1
, E
2
E
3
O
0
–O
7
Address Inputs
Enable Inputs (Active LOW)
Enable Input (Active HIGH)
Outputs (Active LOW)
Description
HIGH/LOW
1.0/1.0
1.0/1.0
1.0/1.0
50/33.3
Input I
IH
/I
IL
Output I
OH
/I
OL
20
µ
A/
−
0.6 mA
20
µ
A/
−
0.6 mA
20
µ
A/
−
0.6 mA
−
1 mA/20 mA
Truth Table
Inputs
E
1
H
X
X
L
L
L
L
L
L
L
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
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
Outputs
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
H
=
HIGH Voltage Level
L
=
LOW Voltage Level
X
=
Immaterial
Functional Description
The F138 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 F138 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 F138 devices and one inverter (See
Figure 1). The F138 can be used as an 8-output demulti-
plexer 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.
FIGURE 1. Expansion to 1-of-32 Decoding
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2
74F138
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.
3
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74F138
Absolute Maximum Ratings
(Note 1)
Storage Temperature
Ambient Temperature under Bias
Junction Temperature under Bias
V
CC
Pin Potential to Ground Pin
Input Voltage (Note 2)
Input Current (Note 2)
Voltage Applied to Output
in HIGH State (with V
CC
=
0V)
Standard Output
3-STATE Output
Current Applied to Output
in LOW State (Max)
ESD Last Passing Voltage (Min)
twice the rated I
OL
(mA)
4000V
−
65
°
C to
+
150
°
C
−
55
°
C to
+
125
°
C
−
55
°
C to
+
150
°
C
−
0.5V to
+
7.0V
−
0.5V to
+
7.0V
−
30 mA to
+
5.0 mA
Recommended Operating
Conditions
Free Air Ambient Temperature
Supply Voltage
0
°
C to
+
70
°
C
+
4.5V to
+
5.5V
−
0.5V to V
CC
−
0.5V to
+
5.5V
Note 1:
Absolute maximum ratings are values beyond which the device
may be damaged or have its useful life impaired. Functional operation
under these conditions is not implied.
Note 2:
Either voltage limit or current limit is sufficient to protect inputs.
DC Electrical Characteristics
Symbol
V
IH
V
IL
V
CD
V
OH
V
OL
I
IH
I
BVI
I
CEX
V
ID
I
OD
I
IL
I
OS
I
CCH
I
CCL
Parameter
Input HIGH Voltage
Input LOW Voltage
Input Clamp Diode Voltage
Output HIGH
Voltage
Output LOW
Voltage
Input HIGH
Current
Input HIGH Current
Breakdown Test
Output HIGH
Leakage Current
Input Leakage
Test
Output Leakage
Circuit Current
Input LOW Current
Output Short-Circuit Current
Power Supply Current
Power Supply Current
−60
13
13
4.75
3.75
−0.6
−150
20
20
5.0
7.0
50
µA
µA
µA
V
µA
mA
mA
mA
mA
Max
Max
Max
0.0
0.0
Max
Max
Max
Max
V
IN
=
2.7V
V
IN
=
7.0V
V
OUT
=
V
CC
I
ID
=
1.9
µA
All Other Pins Grounded
V
IOD
=
150 mV
All Other Pins Grounded
V
IN
=
0.5V
V
OUT
=
0V
V
O
=
HIGH
V
O
=
LOW
10% V
CC
5% V
CC
10% V
CC
2.5
2.7
0.5
Min
2.0
0.8
−1.2
Typ
Max
Units
V
V
V
V
V
Min
Min
Min
V
CC
Conditions
Recognized as a HIGH Signal
Recognized as a LOW Signal
I
IN
= −18
mA
I
OH
= −1
mA
I
OH
= −1
mA
I
OL
=
20 mA
AC Electrical Characteristics
T
A
= +25°C
Symbol
Parameter
Min
t
PLH
t
PHL
t
PLH
t
PHL
t
PLH
t
PHL
Propagation Delay
A
n
to O
n
Propagation Delay
E
1
or E
2
to O
n
Propagation Delay
E
3
to O
n
3.5
4.0
3.5
3.0
4.0
3.5
V
CC
= +5.0V
C
L
=
50 pF
Typ
5.6
6.1
5.4
5.3
6.2
5.6
Max
7.5
8.0
7.0
7.0
8.0
7.5
T
A
=
0°C to
+70°C
V
CC
= +5.0V
C
L
=
50 pF
Min
3.5
4.0
3.5
3.0
4.0
3.5
Max
8.5
9.0
8.0
7.5
9.0
8.5
ns
ns
ns
Units
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4
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