INTEGRATED CIRCUITS
74ALS138
1-of-8 decoder/demultiplexer
Product specification
IC05 Data Handbook
1996 Jul 03
Philips
Semiconductors
Philips Semiconductors
Product specification
1-of-8 decoder/demultiplexer
74ALS138
FEATURES
•
Demultiplexing capability
•
Multiple input enable for easy expansion
•
Ideal for memory chip select decoding
DESCRIPTION
The 74ALS138 decoder accepts three binary weighted inputs (A0,
A1, A2) and when enabled, provides eight mutually exclusive,
active-Low outputs (Q0 – Q7). The device features three Enable
inputs; two active-Low (E0, E1) and one active-High (E2). Every
output will be High unless E0 and E1 are Low and E2 is High. This
multiple enable function allows easy parallel expansion of the device
to 1-of-32 (5 lines to 32 lines) decoder with just four 74ALS138s and
one inverter. The device can be used as an eight output
demultiplexer by using one of the active-Low Enable inputs as the
data input and the remaining Enable inputs as strobes. Enable
inputs not used must be permanently tied to their appropriate
active-High or active-Low state.
TYPICAL
PROPAGATION DELAY
12.0ns
TYPICAL
SUPPLY CURRENT
(TOTAL)
4.0mA
PIN CONFIGURATION
A0
A1
A2
E0
E1
E2
Q7
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
CC
Q0
Q1
Q2
Q3
Q4
Q5
Q6
SF00174
ORDERING INFORMATION
ORDER CODE
DESCRIPTION
COMMERCIAL RANGE
V
CC
= 5V
±10%,
T
amb
= 0°C to +70°C
74ALS138N
74ALS138D
DRAWING
NUMBER
SOT38-4
SOT109-1
TYPE
74ALS138
16-pin plastic DIP
16-pin plastic SO
INPUT AND OUTPUT LOADING AND FAN-OUT TABLE
PINS
A0 – A2
E0, E1
E2
Q0 – Q7
Address inputs
Enable inputs (active-Low)
Enable input (active-High)
Data outputs (active-Low)
DESCRIPTION
74ALS (U.L.)
HIGH/LOW
1.0/1.0
1.0/1.0
1.0/1.0
50/33
LOAD VALUE
HIGH/LOW
20µA/0.1mA
20µA/0.1mA
20µA/0.1mA
1.0mA/20mA
NOTE:
One (1.0) ALS unit load is defined as: 20µA in the High state and 0.1mA in the Low state.
LOGIC SYMBOL
1
2
3
IEC/IEEE SYMBOL
DX
0
2
G
A0 A1 A2
3
2
0
7
0
1
2
3
Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7
4
5
15 14 13 12 11 10
9
7
6
14
13
12
11
1
15
4
5
6
E0
E1
E2
&
10
9
7
V
CC
= Pin 16
GND = Pin 8
SF00175
SC00047
1996 Jul 03
2
853–1848 17016
Philips Semiconductors
Product specification
1-of-8 decoder/demultiplexer
74ALS138
LOGIC DIAGRAM
A2
A1
3
2
A0
1
E0
E1
E2
4
5
6
15
14
13
12
11
10
9
Q1
Q2
Q3
Q4
Q5
Q6
Q0
7
Q7
V
CC
= Pin 16
GND = Pin 8
SF00177
FUNCTION TABLE
INPUTS
E0
H
X
X
L
L
L
L
L
L
L
L
E1
X
H
X
L
L
L
L
L
L
L
L
E2
X
X
L
H
H
H
H
H
H
H
H
A0
X
X
X
L
H
L
H
L
H
L
H
A1
X
X
X
L
L
H
H
L
L
H
H
A2
X
X
X
L
L
L
L
H
H
H
H
Q0
H
H
H
L
H
H
H
H
H
H
H
Q1
H
H
H
H
L
H
H
H
H
H
H
Q2
H
H
H
H
H
L
H
H
H
H
H
OUTPUTS
Q3
H
H
H
H
H
H
L
H
H
H
H
Q4
H
H
H
H
H
H
H
L
H
H
H
Q5
H
H
H
H
H
H
H
H
L
H
H
Q6
H
H
H
H
H
H
H
H
H
L
H
Q7
H
H
H
H
H
H
H
H
H
H
L
H = High voltage level
L = Low voltage level
X = Don’t care
1996 Jul 03
3
Philips Semiconductors
Product specification
1-of-8 decoder/demultiplexer
74ALS138
ABSOLUTE MAXIMUM RATINGS
(Operation beyond the limit set forth in this table may impair the useful life of the device.
Unless otherwise noted these limits are over the operating free-air temperature range.)
SYMBOL
V
CC
V
IN
I
IN
V
OUT
I
OUT
T
amb
T
stg
Supply voltage
Input voltage
Input current
Voltage applied to output in High output state
Current applied to output in Low output state
Operating free-air temperature range
Storage temperature range
PARAMETER
RATING
–0.5 to +7.0
–0.5 to +7.0
–30 to +5
–0.5 to V
CC
16
0 to +70
–65 to +150
UNIT
V
V
mA
V
mA
°C
°C
RECOMMENDED OPERATING CONDITIONS
LIMITS
SYMBOL
V
CC
V
IH
V
IL
I
Ik
I
OH
I
OL
T
amb
Supply voltage
High-level input voltage
Low-level input voltage
Input clamp current
High-level output current
Low-level output current
Operating free-air temperature range
0
PARAMETER
MIN
4.5
2.0
0.8
–18
–0.4
8
+70
NOM
5.0
MAX
5.5
V
V
V
mA
mA
mA
°C
UNIT
DC ELECTRICAL CHARACTERISTICS
(Over recommended operating free-air temperature range unless otherwise noted.)
SYMBOL
V
OH
V
O
OL
V
IK
I
I
I
IH
I
IL
I
O
I
CC
PARAMETER
High-level output voltage
TEST CONDITIONS
1
MIN
V
CC
=
±10%,
V
IL
= MAX,
V
IH
= MIN
V
CC
= MIN, V
IL
= MAX,
,
,
V
IH
= MIN
V
CC
= MIN, I
I
= I
IK
V
CC
= MAX, V
I
= 7.0V
V
CC
= MAX, V
I
= 2.7V
V
CC
= MAX, V
I
= 0.4V
V
CC
= MAX, V
O
= 2.25V
V
CC
= MAX
–30
4
I
OH
= –0.4mA
I
OL
= 4mA
I
OL
= 8mA
V
CC
– 2
0.25
0.35
–0.73
0.40
0.50
–1.5
0.1
20
–0.1
–112
7
LIMITS
TYP
2
UNIT
MAX
V
V
V
V
mA
µA
mA
mA
mA
Low-level
Low level output voltage
Input clamp voltage
Input current at maximum input
voltage
High-level input current
Low-level input current
Output current
3
Supply current (total)
NOTES:
1. For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions for the applicable type.
2. All typical values are at V
CC
= 5V, T
amb
= 25°C.
3. The output conditions have been chosen to produce a current that closely approximates one half of the true short-circuit output current, I
OS
.
1996 Jul 03
4
Philips Semiconductors
Product specification
1-of-8 decoder/demultiplexer
74ALS138
AC ELECTRICAL CHARACTERISTICS
LIMITS
SYMBOL
PARAMETER
TEST CONDITION
T
amb
= 0°C to +70°C
V
CC
= +5.0V
±
10%
C
L
= 50pF, R
L
= 500Ω
MIN
t
PLH
t
PHL
t
PLH
t
PHL
t
PLH
t
PHL
Propagation delay
An to Qn
Propagation delay
E1, E2 to Qn
Propagation delay
E2 to Qn
Waveform 1, 2
Waveform 2
Waveform 1
3.0
3.0
3.0
3.0
3.0
3.0
MAX
22.0
18.0
17.0
17.0
17.0
17.0
ns
ns
ns
UNIT
AC WAVEFORMS
For all waveforms, V
M
= 1.3V.
An, E2
V
M
t
PHL
V
M
t
PLH
An, E0, E1
V
M
t
PHL
V
M
t
PLH
Qn
V
M
V
M
Qn
V
M
V
M
SF00179
SF00180
Waveform 1. Propagation Delay for Inverting Outputs
Waveform 2. Propagation Delay for Non-inverting Outputs
TEST CIRCUIT AND WAVEFORMS
V
CC
NEGATIVE
PULSE
V
IN
PULSE
GENERATOR
R
T
D.U.T.
V
OUT
90%
V
M
10%
t
THL (
t
f
f
)
C
L
R
L
t
w
V
M
10%
t
TLH (
t
r
)
0.3V
90%
AMP (V)
t
TLH (
t
r
)
90%
t
THL (
t
f
)
AMP (V)
90%
V
M
t
w
10%
0.3V
Test Circuit for Totem-pole Outputs
POSITIVE
PULSE
10%
V
M
DEFINITIONS:
R
L
= Load resistor;
see AC electrical characteristics for value.
C
L
= Load capacitance includes jig and probe capacitance;
see AC electrical characteristics for value.
R
T
= Termination resistance should be equal to Z
OUT
of
pulse generators.
Input Pulse Definition
INPUT PULSE REQUIREMENTS
Family
Amplitude V
M
74ALS
3.5V
1.3V
Rep.Rate
1MHz
t
w
500ns
t
TLH
2.0ns
t
THL
2.0ns
SC00005
1996 Jul 03
5
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