1/9
August 2001
s
HIGH SPEED:
t
PD
= 16ns (TYP.) at V
CC
= 4.5V
s
LOW POWER DISSIPATION:
I
CC
= 4
A(MAX.) at T
A
=25C
s
COMPATIBLE WITH TTL OUTPUTS :
V
IH
= 2V (MIN.) V
IL
= 0.8V (MAX)
s
SYMMETRICAL OUTPUT IMPEDANCE:
|I
OH
| = I
OL
= 4mA (MIN)
s
BALANCED PROPAGATION DELAYS:
t
PLH
t
PHL
s
PIN AND FUNCTION COMPATIBLE WITH
74 SERIES 138
DESCRIPTION
The M74HCT138 is an high speed CMOS 3 TO 8
LINE DECODER fabricated with silicon gate
C
2
MOS technology.
If the device is enabled, 3 binary select inputs (A,
B, and C) determine which one of the outputs will
go low. If enable input G1 is held low or either G2A
or G2B is held high, the decoding function is
inhibited and all the 8 outputs go high. Three
enable inputs are provided to ease cascade
connection and application of address decoders
for memory systems.
All inputs are equipped with protection circuits
against static discharge and transient excess
voltage.
M74HCT138
3 TO 8 LINE DECODER (INVERTING)
PIN CONNECTION AND IEC LOGIC SYMBOLS
ORDER CODES
PACKAGE
TUBE
T & R
DIP
M74HCT138B1R
SOP
M74HCT138M1R
M74HCT138RM13TR
TSSOP
M74HCT138TTR
TSSOP
DIP
SOP
M74HCT138
2/9
INPUT AND OUTPUT EQUIVALENT CIRCUIT
PIN DESCRIPTION
TRUTH TABLE
X : Don't Care
LOGIC DIAGRAM
This logic diagram has not be used to estimate propagation delays
PIN No
SYMBOL
NAME AND FUNCTION
1, 2, 3
A, B, C
Address Inputs
4, 5
G2A, G2B
Enable Inputs
6
G1
Enable Input
9, 10, 11, 12,
13, 14, 15,
7
Y0 to Y7
Data Outputs
8
GND
Ground (0V)
16
V
CC
Positive Supply Voltage
INPUTS
OUTPUTS
ENABLE
SELECT
G2B
G2A
G1
C
B
A
Y0
Y1
Y2
Y3
Y4
Y5
Y6
Y7
X
X
L
X
X
X
H
H
H
H
H
H
H
H
X
H
X
X
X
X
H
H
H
H
H
H
H
H
H
X
X
X
X
X
H
H
H
H
H
H
H
H
L
L
H
L
L
L
L
H
H
H
H
H
H
H
L
L
H
L
L
H
H
L
H
H
H
H
H
H
L
L
H
L
H
L
H
H
L
H
H
H
H
H
L
L
H
L
H
H
H
H
H
L
H
H
H
H
L
L
H
H
L
L
H
H
H
H
L
H
H
H
L
L
H
H
L
H
H
H
H
H
H
L
H
H
L
L
H
H
H
L
H
H
H
H
H
H
L
H
L
L
H
H
H
H
H
H
H
H
H
H
H
L
M74HCT138
3/9
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is
not implied
(*) 500mW at 65
C; derate to 300mW by 10mW/
C from 65
C to 85
C
RECOMMENDED OPERATING CONDITIONS
DC SPECIFICATIONS
Symbol
Parameter
Value
Unit
V
CC
Supply Voltage
-0.5 to +7
V
V
I
DC Input Voltage
-0.5 to V
CC
+ 0.5
V
V
O
DC Output Voltage
-0.5 to V
CC
+ 0.5
V
I
IK
DC Input Diode Current
20
mA
I
OK
DC Output Diode Current
20
mA
I
O
DC Output Current
25
mA
I
CC
or I
GND
DC V
CC
or Ground Current
50
mA
P
D
Power Dissipation
500(*)
mW
T
stg
Storage Temperature
-65 to +150
C
T
L
Lead Temperature (10 sec)
300
C
Symbol
Parameter
Value
Unit
V
CC
Supply Voltage
4.5 to 5.5
V
V
I
Input Voltage
0 to V
CC
V
V
O
Output Voltage
0 to V
CC
V
T
op
Operating Temperature
-55 to 125
C
t
r
, t
f
Input Rise and Fall Time (V
CC
= 4.5 to 5.5V)
0 to 500
ns
Symbol
Parameter
Test Condition
Value
Unit
V
CC
(V)
T
A
= 25C
-40 to 85C
-55 to 125C
Min.
Typ.
Max.
Min.
Max.
Min.
Max.
V
IH
High Level Input
Voltage
4.5
to
5.5
2.0
2.0
2.0
V
V
IL
Low Level Input
Voltage
4.5
to
5.5
0.8
0.8
0.8
V
V
OH
High Level Output
Voltage
4.5
I
O
=-20
A
4.4
4.5
4.4
4.4
V
I
O
=-4.0 mA
4.18
4.31
4.13
4.10
V
OL
Low Level Output
Voltage
4.5
I
O
=20
A
0.0
0.1
0.1
0.1
V
I
O
=4.0 mA
0.17
0.26
0.33
0.40
I
I
Input Leakage
Current
5.5
V
I
= V
CC
or GND
0.1
1
1
A
I
CC
Quiescent Supply
Current
5.5
V
I
= V
CC
or GND
4
40
80
A
I
CC
Additional Worst
Case Supply
Current
5.5
Per Input pin
V
I
= 0.5V or
V
I
= 2.4V
Other Inputs at
V
CC
or GND
I
O
= 0
2.0
2.9
3.0
mA
M74HCT138
4/9
AC ELECTRICAL CHARACTERISTICS (C
L
= 50 pF, Input t
r
= t
f
= 6ns)
CAPACITIVE CHARACTERISTICS
1) C
PD
is defined as the value of the IC's internal equivalent capacitance which is calculated from the operating current consumption without
load. (Refer to Test Circuit). Average operating current can be obtained by the following equation. I
CC(opr)
= C
PD
x V
CC
x f
IN
+ I
CC
TEST CIRCUIT
C
L
= 50pF or equivalent (includes jig and probe capacitance)
R
T
= Z
OUT
of pulse generator (typically 50
)
Symbol
Parameter
Test Condition
Value
Unit
V
CC
(V)
T
A
= 25C
-40 to 85C
-55 to 125C
Min.
Typ.
Max.
Min.
Max.
Min.
Max.
t
TLH
t
THL
Output Transition
Time
4.5
8
15
19
22
ns
t
PLH
t
PHL
Propagation Delay
Time (A, B, C - Y)
4.5
17
30
38
45
ns
t
PLH
t
PHL
Propagation Delay
Time (G1 - Y)
4.5
16
30
38
45
ns
t
PLH
t
PHL
Propagation Delay
Time (G2 - Y)
4.5
19
30
38
45
ns
Symbol
Parameter
Test Condition
Value
Unit
V
CC
(V)
T
A
= 25C
-40 to 85C
-55 to 125C
Min.
Typ.
Max.
Min.
Max.
Min.
Max.
C
IN
Input Capacitance
5
10
10
10
pF
C
PD
Power Dissipation
Capacitance (note
1)
52
pF
M74HCT138
5/9
WAVEFORM 1: PROPAGATION DELAYS FOR INVERTING OUTPUTS (f=1MHz; 50% duty cycle)
WAVEFORM 2: PROPAGATION DELAYS FOR NON-INVERTING OUTPUTS (f=1MHz; 50% duty cycle)
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