
SN54F251B, SN74F251B
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDFS066A – MARCH 1987 – REVISED OCTOBER 1993
Copyright 1993, Texas Instruments Incorporated
2–1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
• 3-State Versions of SN54F151B and
SN74F151B
• 3-State Outputs Interface Directly With
System Bus
• Performs Parallel-to-Serial Conversion
• Complementary Outputs Provide True and
Inverted Data
• Package Options Include Plastic
Small-Outline Packages, Ceramic Chip
Carriers, and Standard Plastic and Ceramic
300-mil DIPs
description
These data selectors/multiplexers contain full
binary decoding to select one of eight data
sources and feature strobe-controlled
complementary outputs. The 3-state outputs can
interface with and drive data lines of busorganized systems. When the strobe (G
) input is
high, both outputs are in a high-impedance state
in which both the upper and lower transistors of
each totem-pole output are off, and the output
neither drives nor loads the bus significantly.
The SN54F251B is characterized for operation
over the full military temperature range of –55°C
to 125°C. The SN74F251B is characterized for
operation from 0°C to 70°C.
FUNCTION TABLE
INPUTS
C B A
G
Y W
X X X H Z Z
L LL L D0 D0
L LH L D1 D1
L HL L D2 D2
L HH L D3 D3
H LL L D4 D4
H LH L D5 D5
H HL L D6 D6
H H H L D7 D7
D0, D1, .. . D7 = the level of the respective D input.
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
D3
D2
D1
D0
Y
W
G
GND
V
CC
D4
D5
D6
D7
A
B
C
SN54F251B ...J PACKAGE
SN74F251B ...D OR N PACKAGE
(TOP VIEW)
3212019
910111213
4
5
6
7
8
18
17
16
15
14
D5
D6
NC
D7
A
D1
D0
NC
Y
W
SN54F251B .. . FK PACKAGE
(TOP VIEW)
D2D3NC
C
B
D4
G
GND
NC
NC – No internal connection
V
CC
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.

SN54F251B, SN74F251B
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDFS066A – MARCH 1987 – REVISED OCT OBER 1993
2–2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
logic symbol
†
MUX
EN
7
0
11
A
10
B
2
9
C
0
4
D0
1
3
D1
2
2
D2
3
1
D3
4
15
D4
5
14
D5
6
13
D6
7
12
D7
0
7
G
W
6
Y
5
G
†
This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
Pin numbers shown are for the D, J, and N packages.

SN54F251B, SN74F251B
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDFS066A – MARCH 1987 – REVISED OCTOBER 1993
2–3
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
logic diagram (positive logic)
Data
Select
(Binary)
Data
Inputs
D0
D1
D2
D3
D4
D5
D6
D7
G
W
Y
C
A
B
7
4
3
2
1
15
14
13
12
11
10
9
5
6
Pin numbers shown are for the D, J, and N packages.
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
†
Supply voltage range, V
CC
–0.5 V to 7 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input voltage range (see Note 1) –1.2 V to 7 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input current range –30 mA to 5 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Voltage range applied to any output in the disabled or power-off state –0.5 V to 5.5 V. . . . . . . . . . . . . . . . . . .
Voltage range applied to any output in the high state –0.5 V to V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Current into any output in the low state: SN54F251B 40 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SN74F251B 48 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating free-air temperature range: SN54F251B –55°C to 125°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SN74F251B 0°C to 70°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range –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.
NOTE 1: The input voltage ratings may be exceeded provided the input current ratings are observed.

SN54F251B, SN74F251B
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDFS066A – MARCH 1987 – REVISED OCT OBER 1993
2–4
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
recommended operating conditions
SN54F251B SN74F251B
V
CC
Supply voltage 4.5 5 5.5 4.5 5 5.5 V
V
IH
High-level input voltage 2 2 V
V
IL
Low-level input voltage 0.8 0.8 V
I
IK
Input clamp current –18 –18 mA
I
OH
High-level output current –3 –3 mA
I
OL
Low-level output current 20 24 mA
T
A
Operating free-air temperature –55 125 0 70 °C
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
V
IK
VCC = 4.5 V, II = –18 mA –1.2 –1.2 V
IOH = – 1 mA 2.5 3.4 2.5 3.4
V
OH
IOH = – 3 mA 2.4 3.3 2.4 3.3 V
VCC = 4.75 V , IOH = – 1 mA to –3 mA 2.7
I
OZH
VCC = 5.5 V, VO = 2.7 V 50 50 µA
I
OZL
VCC = 5.5 V, VO = 0.5 V –50 –50 µA
I
I
VCC = 5.5 V, VI = 7 V 0.1 0.1 mA
I
IH
VCC = 5.5 V, VI = 2.7 V 20 20 µA
I
IL
VCC = 5.5 V, VI = 0.5 V – 0.6 – 0.6 mA
I
OS
‡
VCC = 5.5 V, VO = 0 –60 –150 –60 –150 mA
VCC = 5.5 V,
See Note 2
Condition B 16 24 16 24
†
All typical values are at VCC = 5 V, TA = 25°C.
‡
Not more than one output should be shorted at a time, and the duration of the short circuit should not exceed one second.
NOTE 2: ICC is measured with the outputs open under the following conditions:
A. Select input and data input at 4.5 V , output control grounded
B. All inputs at 4.5 V

SN54F251B, SN74F251B
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDFS066A – MARCH 1987 – REVISED OCTOBER 1993
2–5
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
switching characteristics (see Note 3)
PARAMETER
FROM
(INPUT)
TO
(OUTPUT)
VCC = 5 V,
CL = 50 pF,
R1 = 500 Ω,
R2 = 500 Ω,
TA = 25°C
VCC = 4.5 V to 5.5 V,
CL = 50 pF,
R1 = 500Ω,
R2 = 500 Ω,
TA = MIN to MAX
†
UNIT
′F251B SN54F251B SN74F251B
MIN TYP MAX MIN MAX MIN MAX
t
PLH
3.5 5.4 9 3.5 11.5 3.5 9.5
2.5 4.4 7.5 2.5 8 2.5 7.5
4.5 6.2 10.5 3.5 14 4 12.5
2.5 3.8 6 2.5 7.5 2.5 6.5
3.4 4.8 7 2.7 8.5 2.9 8.5
1.9 2.5 5.5 1.7 5.5 1.8 5.5
†
For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions.
NOTE 3: Load circuits and waveforms are shown in Section 1.

SN54F251B, SN74F251B
1-OF-8 DATA SELECTORS/MULTIPLEXERS
WITH 3-STATE OUTPUTS
SDFS066A – MARCH 1987 – REVISED OCT OBER 1993
2–6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

IMPORTANT NOTICE
T exas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue
any product or service without notice, and advise customers to obtain the latest version of relevant information
to verify, before placing orders, that information being relied on is current and complete. All products are sold
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.
CERT AIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF
DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL
APPLICATIONS”). TI SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, AUTHORIZED, OR
WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT DEVICES OR SYSTEMS OR OTHER
CRITICAL APPLICATIONS. INCLUSION OF TI PRODUCTS IN SUCH APPLICA TIONS IS UNDERST OOD TO
BE FULLY AT THE CUSTOMER’S RISK.
In order to minimize risks associated with the customer’s applications, adequate design and operating
safeguards must be provided by the customer to minimize inherent or procedural hazards.
TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent
that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other
intellectual property right of TI covering or relating to any combination, machine, or process in which such
semiconductor products or services might be or are used. TI’s publication of information regarding any third
party’s products or services does not constitute TI’s approval, warranty or endorsement thereof.
Copyright 1998, Texas Instruments Incorporated