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Электронный компонент: 74AC138B

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1/10
April 2001
s
HIGH SPEED: t
PD
= 4.5ns (TYP.) at V
CC
= 5V
s
LOW POWER DISSIPATION:
I
CC
= 4
A(MAX.) at T
A
=25C
s
HIGH NOISE IMMUNITY:
V
NIH
= V
NIL
= 28 % V
CC
(MIN.)
s
50
TRANSMISSION LINE DRIVING
CAPABILITY
s
SYMMETRICAL OUTPUT IMPEDANCE:
|I
OH
| = I
OL
= 24mA (MIN)
s
BALANCED PROPAGATION DELAYS:
t
PLH
t
PHL
s
OPERATING VOLTAGE RANGE:
V
CC
(OPR) = 2V to 6V
s
PIN AND FUNCTION COMPATIBLE WITH
74 SERIES 138
s
IMPROVED LATCH-UP IMMUNITY
DESCRIPTION
The 74AC138 is an advanced high-speed CMOS
3 TO 8 LINE DECODER (INVERTING) fabricated
with sub-micron silicon gate and double-layer
metal wiring C
2
MOS tecnology.
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 to high.
Tree enable inputs are provided to ease cascade
connection and application of address decoders
for memory systems.
All inputs and outputs are equipped with
protection circuits against static discharge, giving
them 2KV ESD immunity and transient excess
voltage.
74AC138
3 TO 8 LINE DECODER (INVERTING)
PIN CONNECTION AND IEC LOGIC SYMBOLS
ORDER CODES
PACKAGE
TUBE
T & R
DIP
74AC138B
SOP
74AC138M
74AC138MTR
TSSOP
74AC138TTR
TSSOP
DIP
SOP
74AC138
2/10
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
15, 14, 13,
12, 11, 10, 9,
7
Y0 to Y7
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
74AC138
3/10
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.
RECOMMENDED OPERATING CONDITIONS
1) V
IN
from 30% to 70% of V
CC
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
50
mA
I
CC
or I
GND
DC V
CC
or Ground Current
400
mA
T
stg
Storage Temperature
-65 to +150
C
T
L
Lead Temperature (10 sec)
300
C
Symbol
Parameter
Value
Unit
V
CC
Supply Voltage
2 to 6
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
dt/dv
Input Rise and Fall Time V
CC
= 3.0, 4.5 or 5.5V (note 1)
8
ns/V
74AC138
4/10
DC SPECIFICATIONS
1) Maximum test duration 2ms, one output loaded at time
2) Incident wave switching is guaranteed on transmission lines with impedances as low as 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.
V
IH
High Level Input
Voltage
3.0
V
O
= 0.1 V or
V
CC
-0.1V
2.1
1.5
2.1
2.1
V
4.5
3.15
2.25
3.15
3.15
5.5
3.85
2.75
3.85
3.85
V
IL
Low Level Input
Voltage
3.0
V
O
= 0.1 V or
V
CC
-0.1V
1.5
0.9
0.9
0.9
V
4.5
2.25
1.35
1.35
1.35
5.5
2.75
1.65
1.65
1.65
V
OH
High Level Output
Voltage
3.0
I
O
=-50
A
2.9
2.99
2.9
2.9
V
4.5
I
O
=-50
A
4.4
4.49
4.4
4.4
5.5
I
O
=-50
A
5.4
5.49
5.4
5.4
3.0
I
O
=-12 mA
2.56
2.46
2.4
4.5
I
O
=-24 mA
3.86
3.76
3.7
5.5
I
O
=-24 mA
4.86
4.76
4.7
V
OL
Low Level Output
Voltage
3.0
I
O
=50
A
0.002
0.1
0.1
0.1
V
4.5
I
O
=50
A
0.001
0.1
0.1
0.1
5.5
I
O
=50
A
0.001
0.1
0.1
0.1
3.0
I
O
=12 mA
0.36
0.44
0.5
4.5
I
O
=24 mA
0.36
0.44
0.5
5.5
I
O
=24 mA
0.36
0.44
0.5
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
OLD
Dynamic Output
Current (note 1, 2)
5.5
V
OLD
= 1.65 V max
75
50
mA
I
OHD
V
OHD
= 3.85 V min
-75
-50
mA
74AC138
5/10
AC ELECTRICAL CHARACTERISTICS (C
L
= 50 pF, R
L
= 500
, Input t
r
= t
f
= 3ns)
(*) Voltage range is 3.3V
0.3V
(**) Voltage range is 5.0V
0.5V
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
/n (per circuit)
TEST CIRCUIT
C
L
= 50pF or equivalent (includes jig and probe capacitance)
R
L
= R
1
= 500
or equivalent
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
PLH
t
PHL
Propagation Delay
Time
A, B, C to Y
3.3
(*)
1.5
5.5
10.5
1.5
14.0
1.5
15.4
ns
5.0
(**)
1.5
4.5
9.0
1.5
10.0
1.5
11.0
t
PLH
t
PHL
Propagation Delay
Time
G1 to Y
3.3
(*)
1.5
6.0
10.5
1.5
14.0
1.5
15.4
ns
5.0
(**)
1.5
4.5
11.0
1.5
10.0
1.5
11.0
t
PLH
t
PHL
Propagation Delay
Time
G2A or G2B to Y
3.3
(*)
1.5
5.5
10.5
1.5
12.7
1.5
14.0
ns
5.0
(**)
1.5
4.5
9.0
1.5
10.0
1.5
10.0
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
5.0
4
pF
C
PD
Power Dissipation
Capacitance
(note 1)
5.0
f
IN
= 10MHz
60
pF