5-1
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)
45678CBGND
D3219AV
CC NC 14 13 12 11 10 9
1234567
16 15
8
D3219
A4
5678CB
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
1234567
16 15
8
EO GS 3 2 1 0
A04
567EIA2A1
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
5-2
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
XXXXXXXXLLHHL
XXXXXXXLHLHHH
XXXXXXLHHHLLL
XXXXXLHHHHLLH
XXXXLHHHHHLHL
XXXLHHHHHHLHH
XXLHHHHHHHHLL
XLHHHHHHHHHLH
LHHHHHHHHHHHL
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
LHHHHHHHHH HH H L
LXXXXXXXL L LL L H
LXXXXXXLHL LH L H
LXXXXXLHHL HL L H
LXXXXLHHHL HH L H
LXXXLHHHHH LL L H
LXXLHHHHHH LH L H
LX LHHHHHHH HL L H
LLHHHHHHHHHH 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
5-3
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
5-4
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)
Sbl
P
Limits
Ui
T C di i
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
V
IL
I
npu
t
LOW
V
o
lt
age 74 0.8
V
pg
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 VCC = MIN, IOH = MAX, VIN = VIH
V
OH
O
u
t
pu
t
HIGH
V
o
lt
age 74 2.7 3.5 V
CC ,OH ,IN IH
or VIL per T ruth Table
VOL
Output LOW Voltage
54, 74 0.25 0.4 V IOL = 4.0 mA VCC = VCC MIN,
VIN =V
IL or VIH
V
OL
O
u
t
pu
t
LOW
V
o
lt
age 74 0.35 0.5 V IOL = 8.0 mA
V
IN =
V
IL or
V
IH
per T ruth Table
IIH
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.
5-5
FAST AND LS TTL DATA
SN54/74LS147 •SN54/74LS148 •SN54/74LS748
AC CHARACTERISTICS (VCC = 5.0 V, T A = 25°C)
SN54/74LS147
Sbl
From To
Wf
Limits
Ui
T C di i
Symbol
From
(Input)
To
(Output) Waveform Min Typ Max Unit Test Conditions
tPLH
Any
Any
In-phase 12 18
ns
C15F
tPHL
A
ny
A
ny
p
output 12 18 ns CL = 15 pF,
tPLH
Any
Any
Out-of-phase 21 33
ns
Lp,
RL = 2.0 kΩ
tPHL
A
ny
A
ny
p
output 15 23 ns
SN54/74LS148
SN54/74LS748
Sbl
From To
Wf
Limits
Ui
T C di i
Symbol
From
(Input)
To
(Output) Waveform Min Typ Max Unit Test Conditions
tPLH
1 thru 7
A0 A1 or A2
In-phase 14 18
ns
C15F
tPHL
1
th
ru
7
A0
,
A1
, or
A2
p
output 15 25 ns
C15F
tPLH
1 thru 7
A0 A1 or A2
Out-of-phase 20 36
ns
C15F
tPHL
1
th
ru
7
A0
,
A1
, or
A2
p
output 16 29 ns
C15F
tPLH
0 thru 7
EO
Out-of-phase 7.0 18
ns
C15F
tPHL
0
th
ru
7
EO
p
output 25 40 ns
C15pF
tPLH
0 thru 7
GS
In-phase 35 55
ns
CL = 15 pF,
R
L
= 2.0 kΩ
tPHL
0
th
ru
7
GS
p
output 9.0 21 ns
RL
=
2
.
0
kΩ
tPLH
EI
A0 A1 or A2
In-phase 16 25
ns
tPHL
EI
A0
,
A1
, or
A2
p
output 12 25 ns
tPLH
EI
GS
In-phase 12 17
ns
tPHL
EI
GS
p
output 14 36 ns
tPLH
EI
EO
In-phase
12 21
tPHL EI EO
I
n-p
h
ase
output 28
30 40
45 ns (LS148)
(LS748)
