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 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.
3212019
910111213
4
5
6
7
8
18
17
16
15
14
GS
3
NC
2
1
6
7
NC
EI
A2
5
4
NC
A0
0V
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
VCC
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
2POST 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
5V18
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
4POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
absolute maximum ratings over operating free-air temperature range†
Supply voltage range, VCC –0.5 V to 7 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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, θJA (see Note 2): D package 113°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
N package 78°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range, Tstg –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 af fect 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
VIInput voltage 0 VCC 0 VCC V
VOOutput voltage 0 VCC 0 VCC V
VCC = 2 V 0 1000 0 1000
ttInput transition (rise and fall) time VCC = 4.5 V 0 500 0 500 ns
VCC = 6 V 0 400 0 400
TAOperating 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
V
CC MIN TYP MAX MIN MAX MIN MAX
UNIT
2 V 1.9 1.998 1.9 1.9
IOH = –20 µA4.5 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 µA4.5 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
IIVI = VCC or 0 6 V ±0.1 ±100 ±1000 ±1000 nA
ICC VI = VCC or 0, IO = 0 6 V 8 160 80 µA
Ci2 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)
PARAMETER
FROM TO
VCC
TA = 25°C SN54HC148 SN74HC148
UNIT
PARAMETER
(INPUT) (OUTPUT)
V
CC MIN TYP MAX MIN MAX MIN MAX
UNIT
2 V 69 180 270 225
1–7 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
07
6 V 17 26 38 33
0
–
7
2 V 75 190 285 240
GS 4.5 V 25 38 57 48
td
6 V 21 32 48 41
ns
t
pd 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
ttAny 4.5 V 8 15 22 19 ns
6 V 6 13 19 16
SN54HC148, SN74HC148
8-LINE TO 3-LINE PRIORITY ENCODERS
SCLS109D – MARCH 1984 – REVISED MAY 1997
6POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
operating characteristics, TA = 25°C
PARAMETER TEST CONDITIONS TYP UNIT
Cpd Power dissipation capacitance No load 35 pF
PARAMETER MEASUREMENT INFORMATION
VOLTAGE WAVEFORM
INPUT RISE AND FALL TIMES
50%50% 10%10% 90% 90% VCC
0 V
trtf
Input
VOLTAGE WAVEFORMS
PROPAGATION DELAY AND OUTPUT TRANSITION TIMES
50%
50%50% 10%10% 90% 90%
VCC
VOH
VOL
0 V
trtf
Input
In-Phase
Output
50%
tPLH tPHL
50% 50%
10% 10% 90%90% VOH
VOL
tr
tf
tPHL tPLH
Out-of-Phase
Output
Test
Point
From Output
Under Test
CL = 50 pF
(see Note A)
LOAD CIRCUIT
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. tPLH and tPHL are the same as tpd.
Figure 1. Load Circuit and Voltage Waveforms
SN54HC148, SN74HC148
8-LINE TO 3-LINE PRIORITY ENCODERS
SCLS109D – MARCH 1984 – REVISED MAY 1997
7
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
01234567EI
EO A0 A1 A2 GS
’HC148
01234567EI
EO A0 A1 A2 GS
’HC148
’HC08
012345678 89101112131415 Enable
(active low)
012 3
Encoded Data (active low)
Priority Flag
(active low)
16-Line Data (active low)
01234567EI
EO A0 A1 A2 GS
’HC148
01234567EI
EO A0 A1 A2 GS
’HC148
’HC00
012345678 89101112131415 Enable
(active low)
012 3
Encoded Data (active high)
Priority Flag
(active high)
16-Line Data (active low)
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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any product or service without notice, and advise customers to obtain the latest version of relevant information
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subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those
pertaining to warranty, patent infringement, and limitation of liability.
TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent
TI deems necessary to support this warranty . Specific testing of all parameters of each device is not necessarily
performed, except those mandated by government requirements.
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DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL
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Copyright 1998, Texas Instruments Incorporated
