DUAL 1-OF-4 DECODER/
DEMULTIPLEXER
The SN54 / 74LS155 and SN54 / 74LS156 are high speed Dual 1-of-4
Decoder/Demultiplexers. These devices have two decoders with common
2-bit Address inputs and separate gated Enable inputs. Decoder “a” has an
Enable gate with one active HIGH and one active LOW input. Decoder “b” has
two active LOW Enable inputs. If the Enable functions are satisfied, one
output of each decoder will be LOW as selected by the address inputs. The
LS156 has open collector outputs for wired-OR (DOT-AND) decoding and
function generator applications.
The LS155 and LS156 are fabricated with the Schottky barrier diode
process for high speed and are completely compatible with all Motorola TTL
families.
SN54/74LS155
SN54/74LS156
DUAL 1-OF-4 DECODER /
DEMULTIPLEXER
LS156-OPEN-COLLECTOR
LOW POWER SCHOTTKY
•
•
•
•
•
•
Schottky Process for High Speed
Multifunction Capability
Common Address Inputs
True or Complement Data Demultiplexing
Input Clamp Diodes Limit High Speed Termination Effects
ESD > 3500 Volts
J SUFFIX
CERAMIC
CASE 620-09
16
1
16
N SUFFIX
PLASTIC
CASE 648-08
1
CONNECTION DIAGRAM DIP
(TOP VIEW)
VCC
16
Eb
15
Eb
14
A0
13
O3b
12
O2b
11
O1b
10
O0b
9
NOTE:
The Flatpak version
has the same pinouts
(Connection Diagram) as
the Dual In-Line Package.
16
1
D SUFFIX
SOIC
CASE 751B-03
ORDERING INFORMATION
1
Ea
2
Ea
3
A1
4
O3a
5
O2a
6
O1a
8
7
O0a GND
SN54LSXXXJ
SN74LSXXXN
SN74LSXXXD
Ceramic
Plastic
SOIC
LOGIC SYMBOL
PIN NAMES
A0, A1
Ea, Eb
Ea
O0 – O3
Address Inputs
Enable (Active LOW) Inputs
Enable (Active HIGH) Input
Active LOW Outputs (Note b)
LOADING
(Note a)
HIGH
0.5 U.L.
0.5 U.L.
0.5 U.L.
10 U.L.
LOW
0.25 U.L.
0.25 U.L.
0.25 U.L.
5 (2.5) U.L.
0
1
1 2
13 3
14 15
E
DECODER a
2
3
A0
A1
A0
A1
0
1
E
DECODER b
2
3
NOTES:
a) 1 TTL Unit Load (U.L.) = 40
µA
HIGH/1.6 mA LOW.
b) The Output LOW drive factor is 2.5 U.L. for Military (54) and 5 U.L. for Commercial (74)
Temperature Ranges. The HIGH level drive for the LS156 must be established by an external
resistor.
7
6
5
4
9
VCC = PIN 16
GND = PIN 8
10 11 12
FAST AND LS TTL DATA
5-1
SN54/74LS155
•
SN54/74LS156
LOGIC DIAGRAM
1
Ea Ea
2
13
A0
A1
3
14
Eb Eb
15
VCC = PIN 16
GND = PIN 8
= PIN NUMBERS
7
6
5
4
9
10
11
12
O0a
O1a
O2a
O3a
O0b
O1b
O2b
O3b
FUNCTIONAL DESCRIPTION
The LS155 and LS156 are Dual 1-of-4 Decoder/Demulti-
plexers with common Address inputs and separate gated
Enable inputs. When enabled, each decoder section accepts
the binary weighted Address inputs (A0, A1) and provides four
mutually exclusive active LOW outputs (O0 – O3). If the Enable
requirements of each decoder are not met, all outputs of that
decoder are HIGH.
Each decoder section has a 2-input enable gate. The
enable gate for Decoder “a” requires one active HIGH input
and one active LOW input (Ea
•E
a). In demultiplexing applica-
tions, Decoder “a” can accept either true or complemented
data by using the Ea or Ea inputs respectively. The enable gate
for Decoder “b” requires two active LOW inputs (Eb
•E
b). The
LS155 or LS156 can be used as a 1-of-8 Decoder/Demulti-
plexer by tying Ea to Eb and relabeling the common connection
as (A2). The other Eb and Ea are connected together to form
the common enable.
The LS155 and LS156 can be used to generate all four
minterms of two variables. These four minterms are useful in
some applications replacing multiple gate functions as shown
in Fig. a. The LS156 has the further advantage of being able to
AND the minterm functions by tying outputs together. Any
number of terms can be wired-AND as shown below.
f = (E + A0 + A1)
⋅
(E + A0 + A1)
⋅
(E + A0 + A1)
⋅
(E + A0 + A1)
where E = Ea + Ea; E = Eb + Eb
E
A0
A1
E
A0
A1
E
A0
A1
E
A0
A1
E
O0 A0
A1
E
O1 A0
A1
E
O2 A0
A1
E
A0
O3
A1
O0
O1
O2
O3
Figure a
TRUTH TABLE
ADDRESS
A0
X
X
L
H
L
H
A1
X
X
L
L
H
H
ENABLE “a”
Ea
L
X
H
H
H
H
Ea
X
H
L
L
L
L
O0
H
H
L
H
H
H
OUTPUT “a”
O1
H
H
H
L
H
H
O2
H
H
H
H
L
H
O3
H
H
H
H
H
L
ENABLE “b”
Eb
H
X
L
L
L
L
Eb
X
H
L
L
L
L
O0
H
H
L
H
H
H
OUTPUT “b”
O1
H
H
H
L
H
H
O2
H
H
H
H
L
H
O3
H
H
H
H
H
L
H = HIGH Voltage Level
L = LOW Voltage Level
X = Don’t Care
FAST AND LS TTL DATA
5-2
SN54/74LS155
GUARANTEED OPERATING RANGES
Symbol
VCC
TA
IOH
IOL
Supply Voltage
Operating Ambient Temperature Range
Output Current — High
Output Current — Low
Parameter
54
74
54
74
54, 74
54
74
Min
4.5
4.75
– 55
0
Typ
5.0
5.0
25
25
Max
5.5
5.25
125
70
– 0.4
4.0
8.0
Unit
V
°C
mA
mA
DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE
(unless otherwise specified)
Limits
Symbol
S b l
VIH
VIL
VIK
VOH
Parameter
P
Input HIGH Voltage
54
Input LOW Voltage
74
Input Clamp Diode Voltage
54
Output HIGH Voltage
74
54, 74
VOL
Output LOW Voltage
74
Input HIGH Current
0.1
Input LOW Current
Short Circuit Current (Note 1)
Power Supply Current
– 20
– 0.4
– 100
10
0.35
0.5
20
IIH
IIL
IOS
ICC
V
µA
mA
mA
mA
mA
2.7
3.5
0.25
0.4
V
V
2.5
– 0.65
3.5
0.8
– 1.5
V
V
Min
2.0
0.7
V
Typ
Max
Unit
U i
V
Test C di i
T
Conditions
Guaranteed Input HIGH Voltage for
All Inputs
Guaranteed Input LOW Voltage for
p
g
All Inputs
VCC = MIN, IIN = – 18 mA
VCC = MIN, IOH = MAX, VIN = VIH
,
,
or VIL per Truth Table
IOL = 4.0 mA
IOL = 8.0 mA
VCC = VCC MIN,
VIN = VIL or VIH
per Truth Table
VCC = MAX, VIN = 2.7 V
VCC = MAX, VIN = 7.0 V
VCC = MAX, VIN = 0.4 V
VCC = MAX
VCC = MAX
Note 1: Not more than one output should be shorted at a time, nor for more than 1 second.
AC CHARACTERISTICS
(TA = 25°C)
Limits
Symbol
S b l
tPLH
tPHL
tPLH
tPHL
tPLH
tPHL
Parameter
P
Propagation Delay
Address, Ea or Eb to Output
Propagation Delay
Address to Output
Propagation Delay
Ea to Output
Min
Typ
10
19
17
19
18
18
Max
15
30
26
30
27
27
Unit
U i
ns
ns
ns
Figure 1
Figure 2
Figure 1
VCC = 5.0 V
50
CL = 15 pF
Test C di i
T
Conditions
AC WAVEFORMS
VIN
1.3 V
tPHL
VOUT
1.3 V
1.3 V
tPLH
1.3 V
VOUT
1.3 V
tPHL
1.3 V
1.3 V
tPLH
1.3 V
VIN
Figure 1
Figure 2
FAST AND LS TTL DATA
5-3
SN54/74LS156
GUARANTEED OPERATING RANGES
Symbol
VCC
TA
VOH
IOL
Supply Voltage
Operating Ambient Temperature Range
Output Voltage — High
Output Current — Low
Parameter
54
74
54
74
54, 74
54
74
Min
4.5
4.75
– 55
0
Typ
5.0
5.0
25
25
Max
5.5
5.25
125
70
5.5
4.0
8.0
Unit
V
°C
V
mA
DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE
(unless otherwise specified)
Limits
Symbol
S b l
VIH
VIL
VIK
IOH
VOL
Parameter
P
Input HIGH Voltage
54
Input LOW Voltage
74
Input Clamp Diode Voltage
Output HIGH Current
Output LOW Voltage
74
Input HIGH Current
0.1
Input LOW Current
Power Supply Current
– 0.4
10
0.35
0.5
20
IIH
IIL
ICC
V
µA
mA
mA
mA
54, 74
54, 74
0.25
– 0.65
0.8
– 1.5
100
0.4
V
µA
V
Min
2.0
0.7
V
Typ
Max
Unit
U i
V
Test C di i
T
Conditions
Guaranteed Input HIGH Voltage for
All Inputs
Guaranteed Input LOW Voltage for
p
g
All Inputs
VCC = MIN, IIN = – 18 mA
VCC = MIN, VOH = MAX
IOL = 4.0 mA
IOL = 8.0 mA
VCC = VCC MIN,
VIN = VIL or VIH
per Truth Table
VCC = MAX, VIN = 2.7 V
VCC = MAX, VIN = 7.0 V
VCC = MAX, VIN = 0.4 V
VCC = MAX
AC CHARACTERISTICS
(TA = 25°C)
Limits
Symbol
S b l
tPLH
tPHL
tPLH
tPHL
tPLH
tPHL
Parameter
P
Propagation Delay
Address, Ea or Eb to Output
Propagation Delay
Address to Output
Propagation Delay
Ea to Output
Min
Typ
25
34
31
34
32
32
Max
40
51
46
51
48
48
Unit
U i
ns
ns
ns
Figure 1
Figure 2
Figure 1
VCC = 5.0 V
50
CL = 15 pF
RL = 2.0 kΩ
Test C di i
T
Conditions
AC WAVEFORMS
VIN
1.3 V
tPHL
VOUT
1.3 V
1.3 V
tPLH
1.3 V
VOUT
1.3 V
tPHL
1.3 V
1.3 V
tPLH
1.3 V
VIN
Figure 1
Figure 2
FAST AND LS TTL DATA
5-4
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