SN54HC148, SN74HC148
8-LINE TO 3-LINE PRIORITY ENCODERS
SCLS109D MARCH 1984 REVISED MAY 1997
1
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
D
Encode Eight Data Lines to 3-Line Binary
(Octal)
D
Applications Include:
n-Bit Encoding
Code Converters and Generators
D
Package Options Include Plastic
Small-Outline (D) and Ceramic Flat (W)
Packages, Ceramic Chip Carriers (FK), and
Standard Plastic (N) and Ceramic (J)
300-mil DIPs
description
The 'HC148 feature priority decoding of the inputs
to ensure that only the highest-order data line is
encoded. These devices encode eight data lines
to 3-line (4-2-1) binary (octal). Cascading circuitry
(enable input EI and enable output EO) has been
provided to allow octal expansion without the
need for external circuitry. Data inputs and outputs
are active at the low logic level.
The SN54HC148 is characterized for operation
over the full military temperature range of 55
C
to 125
C. The SN74HC148 is characterized for
operation from 40
C to 85
C.
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
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
3
2 1 20 19
9 10 11 12 13
4
5
6
7
8
18
17
16
15
14
GS
3
NC
2
1
6
7
NC
EI
A2
5
4
NC
A0
0
V
EO
A1
GND
NC
SN54HC148 . . . FK PACKAGE
(TOP VIEW)
CC
NC No internal connection
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
4
5
6
7
EI
A2
A1
GND
V
CC
EO
GS
3
2
1
0
A0
SN54HC148 . . . J OR W PACKAGE
SN74HC148 . . . D OR N PACKAGE
(TOP VIEW)
Copyright
1997, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
SN54HC148, SN74HC148
8-LINE TO 3-LINE PRIORITY ENCODERS
SCLS109D MARCH 1984 REVISED MAY 1997
2
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
logic symbol
10
1/Z11
11
1
EO
15
2/Z12
12
3/Z13
13
3
GS
14
4/Z14
1
5/Z15
2
5
6/Z16
3
7/Z17
4
7
0
2
4
6
HPRI/BIN
0/Z10
11
13
15
17
10
12
14
16
1
A0
9
A1
7
A2
6
EI
18
1
a
2
a
4
a
5
V18
EN
a
a
This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
Pin numbers shown are for the D, J, N, and W packages.
SN54HC148, SN74HC148
8-LINE TO 3-LINE PRIORITY ENCODERS
SCLS109D MARCH 1984 REVISED MAY 1997
3
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
logic diagram (positive logic)
11
A0
9
1
A1
7
A2
6
GS
14
EO
15
12
2
13
3
1
4
2
5
5
EI
4
7
3
6
10
0
Pin numbers shown are for the D, J, N, and W packages.
SN54HC148, SN74HC148
8-LINE TO 3-LINE PRIORITY ENCODERS
SCLS109D MARCH 1984 REVISED MAY 1997
4
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
absolute maximum ratings over operating free-air temperature range
Supply voltage range, V
CC
0.5 V to 7 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input clamp current, I
IK
(V
I
< 0 or V
I
> V
CC
) (see Note 1)
20 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output clamp current, I
OK
(V
O
< 0 or V
O
> V
CC
) (see Note 1)
20 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous output current, I
O
(V
O
= 0 to V
CC
)
25 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous current through V
CC
or GND
50 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Package thermal impedance,
JA
(see Note 2): D package
113
C/W
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
N package
78
C/W
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range, T
stg
65
C to 150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTES:
1. The input and output voltage ratings may be exceeded if the input and output current ratings are observed.
2. The package thermal impedance is calculated in accordance with JESD 51, except for through-hole packages, which use a trace
length of zero.
recommended operating conditions
SN54HC148
SN74HC148
UNIT
MIN
NOM
MAX
MIN
NOM
MAX
UNIT
VCC
Supply voltage
2
5
6
2
5
6
V
VCC = 2 V
1.5
1.5
VIH
High-level input voltage
VCC = 4.5 V
3.15
3.15
V
VCC = 6 V
4.2
4.2
VCC = 2 V
0
0.5
0
0.5
VIL
Low-level input voltage
VCC = 4.5 V
0
1.35
0
1.35
V
VCC = 6 V
0
1.8
0
1.8
VI
Input voltage
0
VCC
0
VCC
V
VO
Output voltage
0
VCC
0
VCC
V
VCC = 2 V
0
1000
0
1000
tt
Input transition (rise and fall) time
VCC = 4.5 V
0
500
0
500
ns
VCC = 6 V
0
400
0
400
TA
Operating free-air temperature
55
125
40
85
C
SN54HC148, SN74HC148
8-LINE TO 3-LINE PRIORITY ENCODERS
SCLS109D MARCH 1984 REVISED MAY 1997
5
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
PARAMETER
TEST CONDITIONS
VCC
TA = 25
C
SN54HC148
SN74HC148
UNIT
PARAMETER
TEST CONDITIONS
VCC
MIN
TYP
MAX
MIN
MAX
MIN
MAX
UNIT
2 V
1.9
1.998
1.9
1.9
IOH = 20
A
4.5 V
4.4
4.499
4.4
4.4
VOH
VI = VIH or VIL
6 V
5.9
5.999
5.9
5.9
V
IOH = 4 mA
4.5 V
3.98
4.3
3.7
3.84
IOH = 5.2 mA
6 V
5.48
5.8
5.2
5.34
2 V
0.002
0.1
0.1
0.1
IOL = 20
A
4.5 V
0.001
0.1
0.1
0.1
VOL
VI = VIH or VIL
6 V
0.001
0.1
0.1
0.1
V
IOL = 4 mA
4.5 V
0.17
0.26
0.4
0.33
IOL = 5.2 mA
6 V
0.15
0.26
0.4
0.33
II
VI = VCC or 0
6 V
0.1
100
1000
1000
nA
ICC
VI = VCC or 0,
IO = 0
6 V
8
160
80
A
Ci
2 V to 6 V
3
10
10
10
pF
switching characteristics over recommended operating free-air temperature range, C
L
= 50 pF
(unless otherwise noted) (see Figure 1)
PARAMETER
FROM
TO
VCC
TA = 25
C
SN54HC148
SN74HC148
UNIT
PARAMETER
(INPUT)
(OUTPUT)
VCC
MIN
TYP
MAX
MIN
MAX
MIN
MAX
UNIT
2 V
69
180
270
225
17
A0, A1, or A2
4.5 V
23
36
54
45
6 V
21
31
46
38
2 V
60
150
225
190
EO
4.5 V
20
30
45
38
0 7
6 V
17
26
38
33
07
2 V
75
190
285
240
GS
4.5 V
25
38
57
48
t d
6 V
21
32
48
41
ns
tpd
2 V
78
195
295
245
ns
A0, A1, or A2
4.5 V
26
39
59
49
6 V
22
33
50
42
2 V
57
145
220
180
EI
GS
4.5 V
19
29
44
36
6 V
16
25
38
31
2 V
66
165
250
205
EO
4.5 V
22
33
50
41
6 V
19
28
43
35
2 V
28
75
110
95
tt
Any
4.5 V
8
15
22
19
ns
6 V
6
13
19
16
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