5-245
FAST AND LS TTL DATA
10-LINE-TO-4-LINE
AND 8-LINE-TO-3-LINE
PRIORITY ENCODERS
The SN54/74LS147 and the SN54/74LS148 are Priority Encoders. They
provide priority decoding of the inputs to ensure that only the highest order
data line is encoded. Both devices have data inputs and outputs which are
active at the low logic level.
The LS147 encodes nine data lines to four-line (8-4-2-1) BCD. The implied
decimal zero condition does not require an input condition because zero is
encoded when all nine data lines are at a high logic level.
The LS148 encodes eight data lines to three-line (4-2-1) binary (octal). By
providing cascading circuitry (Enable Input EI and Enable Output EO) octal
expansion is allowed without needing external circuitry.
The SN54/74LS748 is a proprietary Motorola part incorporating a built-in
deglitcher network which minimizes glitches on the GS output. The glitch
occurs on the negative going transition of the EI input when data inputs 0–7
are at logical ones.
The only dc parameter differences between the LS148 and the LS748 are
that (1) Pin 10 (input 0) has a fan-in of 2 on the LS748 versus a fan-in of 1 on
the LS148; (2) Pins 1, 2, 3, 4, 11, 12 and 13 (inputs 1, 2, 3, 4, 5, 6, 7) have a
fan-in of 3 on the LS748 versus a fan-in of 2 on the LS148.
The only ac difference is that tPHL from EI to EO is changed from 40 to
45 ns. SN54/74LS147
(TOP VIEW)
SN54/74LS148
SN54/74LS748
(TOP VIEW)
4 5 6 7 8 C B GND
D 3 2 1 9 AVCC NC
14 13 12 11 10 9
1234567
16 15
8
D 3 2 1 9
A4
5 6 7 8 C B
OUTPUT INPUTS OUTPUT
INPUTS OUTPUTS
4 5 6 7 E1 A2 A1 GND
VCC EO GS 3 2 1 0 A0
14 13 12 11 10 9
1 2 3 4 5 6 7
16 15
8
EO GS 3 2 1 0
A04
5 6 7 EI A2 A1
OUTPUTS INPUTS OUTPUT
INPUTS OUTPUTS
SN54/74LS147
SN54/74LS148
SN54/74LS748
10-LINE-TO-4-LINE
AND 8-LINE-TO-3-LINE
PRIORITY ENCODERS
LOW POWER SCHOTTKY
J SUFFIX
CERAMIC
CASE 620-09
N SUFFIX
PLASTIC
CASE 648-08
16 1
16
1
ORDERING INFORMATION
SN54LSXXXJ Ceramic
SN74LSXXXN Plastic
SN74LSXXXD SOIC
16 1
D SUFFIX
SOIC
CASE 751B-03
5-246
FAST AND LS TTL DATA
SN54/74LS147 • SN54/74LS148 • SN54/74LS748
SN54/74LS147
FUNCTION TABLE
INPUTS OUTPUTS
1 2 3 4 5 6 7 8 9 D C B A
H H H H H H H H H H H H H
X X X X X X X X L L H H L
X X X X X X X L H L H H H
X X X X X X L H H H L L L
X X X X X L H H H H L L H
X X X X L H H H H H L H L
X X X L H H H H H H L H H
X X L H H H H H H H H L L
X L H H H H H H H H H L H
L H H H H H H H H H H H L
SN54/74LS148
SN54/74LS748
FUNCTION TABLE
INPUTS OUTPUTS
EI 0 1 2 3 4 5 6 7 A2 A1 A0 GS EO
H X X X X X X X X H H H H H
L H H H H H H H H H H H H L
L X X X X X X X L L L L L H
L X X X X X X L H L L H L H
L X X X X X L H H L H L L H
L X X X X L H H H L H H L H
L X X X L H H H H H L L L H
L X X L H H H H H H L H L H
L X L H H H H H H H H L L H
L L H H H H H H H H H H L H
H = HIGH Logic Level, L = LOW Logic Level, X = Irrelevant
FUNCTIONAL BLOCK DIAGRAMS
SN54/74LS147 SN54/74LS148
1
2
3
4
5
6
7
8
9
(11)
(12)
(13)
(1)
(2)
(3)
(4)
(5)
(10)
(9)
(7)
(6)
(14)
A
B
C
D
0
1
2
3
4
5
6
7
EI
(10)
(11)
(12)
(13)
(1)
(2)
(3)
(4)
(5)
(15) EO
(14) GS
(8) A0
(7) A1
(6) A2
5-247
FAST AND LS TTL DATA
SN54/74LS147 • SN54/74LS148 • SN54/74LS748
FUNCTIONAL BLOCK DIAGRAMS (continued)
SN54/74LS748
G31
G2
G3
G4
G5
G6
G7
G8
G1
G9
G10
G11
G12
G13
0
1
2
3
4
5
6
7
EI
(10)
(11)
(12)
(13)
(1)
(2)
(3)
(4)
(5)
(15) EO
(14) GS
(9) A0
(7) A1
(6) A2
G29
G18
G23
G28
5-248
FAST AND LS TTL DATA
SN54/74LS147 • SN54/74LS148 • SN54/74LS748
GUARANTEED OPERATING RANGES
Symbol Parameter Min Typ Max Unit
VCC Supply Voltage 54
74 4.5
4.75 5.0
5.0 5.5
5.25 V
TAOperating Ambient Temperature Range 54
74 –55
025
25 125
70 °C
IOH Output Current — High 54, 74 –0.4 mA
IOL Output Current — Low 54
74 4.0
8.0 mA
DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified)
Symbol
Parameter
Limits
Unit
Test Conditions
Symbol
Parameter
Min Typ Max
Unit
Test Conditions
VIH Input HIGH Voltage 2.0 V Guaranteed Input HIGH Voltage for
All Inputs
VIL
Input LOW Voltage
54 0.7
V
Guaranteed Input LOW Voltage for
All Inputs
VIL
Input LOW Voltage
74 0.8
V
Guaranteed Input LOW Voltage for
All Inputs
VIK Input Clamp Diode Voltage –0.65 –1.5 V VCC = MIN, IIN = –18 mA
VOH
Output HIGH Voltage
54 2.5 3.5 V
V
CC = MIN, IOH = MAX, VIN = VIH
or VIL per Truth Table
VOH
Output HIGH Voltage
74 2.7 3.5 V
VCC = MIN, IOH = MAX, VIN = VIH
or VIL per Truth Table
VOL
Output LOW Voltage
54, 74 0.25 0.4 V IOL = 4.0 mA
VCC = VCC MIN,
VIN = VIL or VIH
per Truth Table
VOL
Output LOW Voltage
74 0.35 0.5 V IOL = 8.0 mA
VIN = VIL or VIH
per Truth Table
I
IH
Input HIGH Current
All Others
Input 0 (LS748)
Inputs 1–7 (LS148)
Inputs 1–7 (LS748)
20
40
40
60
µA VCC = MAX, VIN = 2.7 V
IIH
All Others
Input 0 (LS748)
Inputs 1–7 (LS148)
Inputs 1–7 (LS748)
0.1
0.2
0.2
0.3
mA VCC = MAX, VIN = 7.0 V
IIL
Input LOW Current
All Others
Input 0 (LS748)
Inputs 1–7 (LS148)
Inputs 1–7 (LS748)
–0.4
–0.8
–0.8
–1.2
mA VCC = MAX, VIN = 0.4 V
IOS Short Circuit Current (Note 1) –20 –100 mA VCC = MAX
ICCH Power Supply Current Output HIGH 17 mA VCC = MAX, All Inputs = 4.5 V
ICCL Output LOW 20 mA VCC = MAX, Inputs 7 & E1 = GND
All Other Inputs = 4.5 V
Note 1: Not more than one output should be shorted at a time, nor for more than 1 second.
5-249
FAST AND LS TTL DATA
SN54/74LS147 • SN54/74LS148 • SN54/74LS748
AC CHARACTERISTICS (VCC = 5.0 V, TA = 25°C)
SN54/74LS147
Symbol
From
(Input)
To
(Output)
Waveform
Limits
Unit
Test Conditions
Symbol
From
(Input)
To
(Output)
Waveform
Min Typ Max
Unit
Test Conditions
tPLH
Any
Any
In-phase
output
12 18
ns
CL = 15 pF,
RL = 2.0 kΩ
tPHL
Any
Any
In-phase
output
12 18
ns
C
L = 15 pF,
RL = 2.0 kΩ
tPLH
Any
Any
Out-of-phase
output
21 33
ns
CL = 15 pF,
RL = 2.0 kΩ
tPHL
Any
Any
Out-of-phase
output
15 23
ns
SN54/74LS148
SN54/74LS748
Symbol
From
(Input)
To
(Output)
Waveform
Limits
Unit
Test Conditions
Symbol
From
(Input)
To
(Output)
Waveform
Min Typ Max
Unit
Test Conditions
tPLH
1 thru 7
A0, A1, or A2
In-phase
output
14 18
ns
CL = 15 pF,
RL = 2.0 kΩ
tPHL
1 thru 7
A0, A1, or A2
In-phase
output
15 25
ns
CL = 15 pF,
RL = 2.0 kΩ
tPLH
1 thru 7
A0, A1, or A2
Out-of-phase
output
20 36
ns
CL = 15 pF,
RL = 2.0 kΩ
tPHL
1 thru 7
A0, A1, or A2
Out-of-phase
output
16 29
ns
CL = 15 pF,
RL = 2.0 kΩ
tPLH
0 thru 7
EO
Out-of-phase
output
7.0 18
ns
CL = 15 pF,
RL = 2.0 kΩ
tPHL
0 thru 7
EO
Out-of-phase
output
25 40
ns
CL = 15 pF,
RL = 2.0 kΩ
tPLH
0 thru 7
GS
In-phase
output
35 55
ns
CL = 15 pF,
RL = 2.0 kΩ
tPHL
0 thru 7
GS
In-phase
output
9.0 21
ns
RL = 2.0 kΩ
tPLH
EI
A0, A1, or A2
In-phase
output
16 25
ns
tPHL
EI
A0, A1, or A2
In-phase
output
12 25
ns
tPLH
EI
GS
In-phase
output
12 17
ns
tPHL
EI
GS
In-phase
output
14 36
ns
tPLH
EI
EO
In-phase
output
12 21
ns
tPHL
EI EO
In-phase
output
28
30 40
45
ns
(LS148)
(LS748)
5-250
FAST AND LS TTL DATA
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16-Pin Plastic
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5-251
FAST AND LS TTL DATA
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