Datasheet SN54HC148J, SN74HC148DR, SN74HC148DW, SN74HC148DWR, SN74HC148N Datasheet (Texas Instruments)

SN54HC148, SN74HC148

8-LINE TO 3-LINE PRIORITY ENCODERS

SCLS109D – MARCH 1984 – REVISED MA Y 1997

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.

SN54HC148 ...J OR W PACKAGE
SN74HC148 . . . D OR N PACKAGE

SN54HC148 . . . FK PACKAGE

6
7

NC

EI

A2

NC – No internal connection

(TOP VIEW)

4

1

5

2

6

3

7

4
5

EI

6

A2

7

A1

GND

8

(TOP VIEW)

54NC

3212019

4
5
6
7
8

910111213

A1

GND

NC

16
15
14
13
12
11
10

9

CC

V

A0

V
EO
GS
3
2
1
0
A0

EO

18
17
16
15
14

0

CC

GS
3
NC
2
1

FUNCTION TABLE

INPUTS

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 HHHHHHHHHHHL
L X XXXXXXLLLLLH
L X XXXXXLHLLHLH

L X XXXXLHHLHLLH
L X XXXLHHHLHHLH
L X XXLHHHHHLLLH
L X XLHHHHHHLHLH
L X LHHHHHHHHLLH
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.

OUTPUTS

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.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

Copyright  1997, Texas Instruments Incorporated

1

SN54HC148, SN74HC148
8-LINE TO 3-LINE PRIORITY ENCODERS

SCLS109D – MARCH 1984 – REVISED MA Y 1997

logic symbol

†

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.

†

a

HPRI/BIN

10

11

12

13

14

15

16

17

≥1

10

0

11

1

12

2

13

3

1

4

2

5

3

6

4

7

5

EI

0/Z10
1/Z11
2/Z12
3/Z13
4/Z14
5/Z15
6/Z16
7/Z17

V18
EN

18

1
2
4

15

EO

a

a
a
a

14

GS

9

A0

7

A1

6

A2

2

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logic diagram (positive logic)

10

0

11

1

12

2

13

3

SN54HC148, SN74HC148

8-LINE TO 3-LINE PRIORITY ENCODERS

SCLS109D – MARCH 1984 – REVISED MA Y 1997

15

EO

14

GS

9

A0

1

4

7

A1

2

5

3

6

4

7

5

EI

6

A2

Pin numbers shown are for the D, J, N, and W packages.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

3

SN54HC148, SN74HC148

UNIT

8-LINE TO 3-LINE PRIORITY ENCODERS

SCLS109D – MARCH 1984 – REVISED MA Y 1997

absolute maximum ratings over operating free-air temperature range

Supply voltage range, V

–0.5 V to 7 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CC

†

Input clamp current, IIK (VI < 0 or VI > VCC) (see Note 1) ±20 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Output clamp current, IOK (VO < 0 or VO > VCC) (see Note 1) ±20 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Continuous output current, IO (VO = 0 to VCC) ±25 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Continuous current through VCC or GND ±50 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Package thermal impedance, θ

(see Note 2): D package 113°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

JA

N package 78°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Storage temperature range, T

†

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.

–65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

stg

recommended operating conditions

SN54HC148 SN74HC148

MIN NOM MAX MIN NOM MAX

V

V

V

V
V

t

t

T

Supply voltage 2 5 6 2 5 6 V

CC

VCC = 2 V 1.5 1.5

High-level input voltage

IH

Low-level input voltage

IL

Input voltage 0 V

I

Output voltage 0 V

O

Input transition (rise and fall) time

Operating free-air temperature –55 125 –40 85 °C

A

VCC = 4.5 V
VCC = 6 V 4.2 4.2
VCC = 2 V 0 0.5 0 0.5
VCC = 4.5 V
VCC = 6 V 0 1.8 0 1.8

VCC = 2 V 0 1000 0 1000
VCC = 4.5 V
VCC = 6 V 0 400 0 400

3.15 3.15

0 1.35 0 1.35

CC
CC

0 500 0 500

0 V
0 V

CC
CC

V

V

V
V

ns

4

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PARAMETER

TEST CONDITIONS

V

UNIT

PARAMETER

V

UNIT

0–7

t

ns

SN54HC148, SN74HC148

8-LINE TO 3-LINE PRIORITY ENCODERS

SCLS109D – MARCH 1984 – REVISED MA Y 1997

electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)

TA = 25°C SN54HC148 SN74HC148

MIN TYP MAX MIN MAX MIN MAX

V

V

V

V

I
I
C

OH

OL

I
CC

i

CC

2 V 1.9 1.998 1.9 1.9

IOH = –20 µA

VI = VIH or V

VI = VIH or V

VI = VCC or 0 6 V ±0.1 ±100 ±1000 ±1000 nA
VI = VCC or 0, IO = 0 6 V 8 160 80 µA

IL

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

IOL = 20 µA

IL

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

4.5 V 4.4 4.499 4.4 4.4
6 V 5.9 5.999 5.9 5.9

2 V 0.002 0.1 0.1 0.1

4.5 V 0.001 0.1 0.1 0.1
6 V 0.001 0.1 0.1 0.1

2 V to 6 V 3 10 10 10 pF

switching characteristics over recommended operating free-air temperature range, CL = 50 pF
(unless otherwise noted) (see Figure 1)

FROM TO

(INPUT) (OUTPUT)

1–7 A0, A1, or A2

EO

GS

pd

A0, A1, or A2

EI GS

EO

t

t

Any

CC

2 V 69 180 270 225

4.5 V 23 36 54 45
6 V 21 31 46 38
2 V 60 150 225 190

4.5 V 20 30 45 38
6 V 17 26 38 33
2 V 75 190 285 240

4.5 V 25 38 57 48
6 V 21 32 48 41
2 V 78 195 295 245

4.5 V 26 39 59 49
6 V 22 33 50 42
2 V 57 145 220 180

4.5 V 19 29 44 36
6 V 16 25 38 31
2 V 66 165 250 205

4.5 V 22 33 50 41
6 V 19 28 43 35
2 V 28 75 110 95

4.5 V 8 15 22 19
6 V 6 13 19 16

TA = 25°C SN54HC148 SN74HC148

MIN TYP MAX MIN MAX MIN MAX

ns

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5

SN54HC148, SN74HC148
8-LINE TO 3-LINE PRIORITY ENCODERS

SCLS109D – MARCH 1984 – REVISED MA Y 1997

operating characteristics, TA = 25°C

PARAMETER TEST CONDITIONS TYP UNIT

C

Input

Power dissipation capacitance No load 35 pF

pd

PARAMETER MEASUREMENT INFORMATION

From Output

Under Test

LOAD CIRCUIT

90% 90%

t

r

Test
Point

CL = 50 pF
(see Note A)

V

50%50%

CC

10%10%

0 V

t

f

Input

In-Phase

Output

Out-of-Phase

Output

50%

t

t

PLH

PHL

50%

t

PHL

90% 90%

t

r

t

PLH

50% 50%

10% 10%

t

f

V

CC

0 V

V

50%50%

OH

10%10%

V

OL

t

f

V

OH

90%90%

V

OL

t

r

VOLTAGE WAVEFORM

INPUT RISE AND FALL TIMES

NOTES: A. CL includes probe and test-fixture capacitance.

B. Phase relationships between waveforms were chosen arbitrarily. All input pulses are supplied by generators having the following

characteristics: PRR ≤ 1 MHz, ZO = 50 Ω, tr = 6 ns, tf = 6 ns.
C. The outputs are measured one at a time with one input transition per measurement.
D. t

PLH

and t

are the same as tpd.

PHL

Figure 1. Load Circuit and Voltage Waveforms

PROPAGATION DELAY AND OUTPUT TRANSITION TIMES

VOLTAGE WAVEFORMS

6

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SN54HC148, SN74HC148

8-LINE TO 3-LINE PRIORITY ENCODERS

SCLS109D – MARCH 1984 – REVISED MA Y 1997

APPLICATION INFORMATION

16-Line Data (active low)

012345678 89101112131415

01234567EI

’HC148

EO A0 A1 A2 GS

012 3

Encoded Data (active low)

16-Line Data (active low)

012345678 89101112131415

01234567EI

’HC148

EO A0 A1 A2 GS

’HC08

Priority Flag

(active low)

Enable
(active low)

Enable
(active low)

01234567EI

’HC148

EO A0 A1 A2 GS

012 3

Encoded Data (active high)

01234567EI

’HC148

EO A0 A1 A2 GS

’HC00

Priority Flag

(active high)

Figure 2. Priority Encoder for 16 Bits

Since the ’HC148 is a combinational logic circuit, wrong addresses can appear during input transients. Moreover, a
change from high to low at EI can cause a transient low on GS when all inputs are high. This must be considered when
strobing the outputs.

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7

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