Philips 74als138 DATASHEETS
INTEGRATED CIRCUITS
74ALS138
1-of-8 decoder/demultiplexer
Product specification 1996 Jul 03
IC05 Data Handbook
Philips Semiconductors Product specification
74ALS1381-of-8 decoder/demultiplexer
FEA TURES
PIN CONFIGURATION
•Demultiplexing capability
1
•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 (Q
inputs; two active-Low (E
output will be High unless E
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.
TYPE
74ALS138 12.0ns 4.0mA
INPUT AND OUTPUT LOADING AND FAN-OUT TABLE
PINS DESCRIPTION
A0 – A2 Address inputs 1.0/1.0 20µA/0.1mA
E0, E1 Enable inputs (active-Low) 1.0/1.0 20µA/0.1mA
E2 Enable input (active-High) 1.0/1.0 20µA/0.1mA
Q0 – Q7 Data outputs (active-Low) 50/33 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.
0 – Q7). The device features three Enable
0, E1) and one active-High (E2). Every
0 and E1 are Low and E2 is High. This
TYPICAL
PROPAGATION DELAY
TYPICAL
SUPPLY CURRENT
(TOTAL)
ORDERING INFORMA TION
DESCRIPTION COMMERCIAL RANGE
16-pin plastic DIP 74ALS138N SOT38-4
16-pin plastic SO 74ALS138D SOT109-1
A0
2
A1
3
A2
4
E
0
5
E
1
6
E2
7
Q
74ALS (U.L.)
HIGH/LOW
ORDER CODE
V
= 5V ±10%,
CC
T
= 0°C to +70°C
amb
16
V
CC
0
15
Q
Q
14
1
13
2
Q
12
Q3
11
Q4
107
Q5
98GND Q6
LOAD VALUE
HIGH/LOW
SF00174
DRAWING
NUMBER
LOGIC SYMBOL
123
4
5
6
VCC = Pin 16
GND = Pin 8
E0
E1
E2
Q114Q0
15
1996 Jul 03 853–1848 17016
A1 A2A0
Q2 Q3 Q4 Q5
13 12 11 10
Q69Q7
7
SF00175
IEC/IEEE SYMBOL
2
1
2
3
4
5
6
DX
0
G
2
0
0
1
7
2
3
&
15
14
13
12
11
10
9
7
SC00047
Philips Semiconductors Product specification
74ALS1381-of-8 decoder/demultiplexer
LOGIC DIAGRAM
3
A2
2
A1
1
A0
4
0
E
5
1
E
6
E2
15 14 13 12 11 10 9 7
0Q1Q2Q3Q4Q5Q6Q7
Q
V
= Pin 16
CC
GND = Pin 8
FUNCTION TABLE
INPUTS OUTPUTS
E0 E1 E2 A0 A1 A2 Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7
H X X 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
X X L 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 H L L 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 H H L H H H L H H H H
L L H L L H 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 L H H H H H H H H L H
L L H H H H H H H H H H H L
H = High voltage level
L = Low voltage level
X = Don’t care
SF00177
1996 Jul 03
3
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