Fairchild Semiconductor DM74LS257BN, DM74LS257BM, DM74LS257BCW Datasheet
© 1999 Fairchild Semiconductor Corporation DS006417 www.fairchildsemi.com
June 1989
Revised November 1999
DM74LS257B 3-STATE Quad 2-Data Selectors/Multiplexers
DM74LS257B
3-STATE Quad 2-Data Selectors/Multiplexers
General Description
These Schottky-clamped high-performance multiplexers
feature 3-STATE outputs that can interface directly with
data lines of bus-organized systems. With all but one of the
common outputs disabl ed (a t a h igh imp edance state) , the
low impedance of the single enabled output will drive the
bus line to a HIGH or LOW logic level. To minimize the possibility that two outputs will attempt to take a common bus
to opposite logic levels, the output enable circuitry is
designed such that the output disable times are shorter
than the output enable times.
This 3-STATE output feature means that n-bi t (paralleled)
data selectors with up to 258 sou rces can be impl ement ed
for data buses. It also permits the use of standard TTL registers for data retention throughout the system.
Features
■ 3-STATE versions LS157 and LS158 with same pinouts
■ Schottky-clamped for significant improvement in A-C
performance
■ Provides bus interface from multiple sources in
high-performance systems
■ Average propagation delay from data input 12 ns
■ Typical power di ssipation: 50 mW
Ordering Code:
Devices also availab le in Tape and Reel. Specify by appending th e s uffix let t er “X” to the ordering code.
Connection Diagram
Function Table
H = HIGH Level X = Don’t Care
L = LOW Level Z = High Impedanc e (off)
Logic Diagram
Order Number Package Number Package Description
DM74LS257BM M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
DM74LS257BN N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Inputs Output Y
Output
Select A B LS257
Control
HXXXZ
LLLXL
LLHXH
LHXLL
LHXHH
www.fairchildsemi.com 2
DM74LS257B
Absolute Maximum Ratings(Note 1)
Note 1: The “Absolute Maximum Ratings” are those values beyon d which
the safety of the device cannot be guaranteed. the device should not be
operated at these limit s. The parametric values defin ed in the Electrical
Characteristics tables are not guaranteed at the absolute maximum ratings.
The Recommended Operating Conditions table will define the conditions
for actual device operation.
Recommended Operating Conditions
DC Electrical Characteristics
Note 2: All typicals are at VCC = 5V, TA = 25°C.
Note 3: Not more than one output should be shorted at a t im e, and the duration should not exceed one second.
Note 4: I
CC
is measured with all out puts open and all possib l e inputs grounded, whil e ac hieving the stated outp ut co nditions.
Supply Voltage 7V
Input Voltage 7V
Operating Free Air Temperature Range 0°C to +70°C
Storage Temperature Range −65°C to +150°C
Symbol Parameter Min Nom Max Units
V
CC
Supply Voltage 4.75 5 5.25 V
V
IH
HIGH Level Input Voltage 2 V
V
IL
LOW Level Input Voltage 0.8 V
I
OH
HIGH Level Output Current −2.6 mA
I
OL
LOW Level Output Current 24 mA
T
A
Free Air Operating Temperature 0 70 °C
Symbol Parameter Conditions Min
Typ
Max Units
(Note 2)
V
I
Input Clamp Voltage VCC = Min, II = −18 mA −1.5 V
V
OH
HIGH Level Output Voltage VIL = Max, VIH = Min 2.4 3.1 V
V
OL
LOW Level Output VIL = Max, VIH = Min 0.35 0.5
V
Voltage IOL = 12 mA, VCC = Min 0.25 0.4
I
I
Input Current @ Max VCC = Max, Select 0.2
mA
Input Voltage V
I
= 7V Other 0.1
I
IH
HIGH Level Input VCC = Max, Select 40
µA
Current V
I
= 2.7V Other 20
I
IL
LOW Level Input VCC = Max, Select −0.8
mA
Current VI = 0.4V Other −0.4
I
OZH
OFF-State Output Current with VCC = Max, VO = 2.7V
20 µA
HIGH Level Output Voltage Applied V
IH
= Min, VIL = Max
I
OZL
OFF-State Output Current with VCC = Max, VO = 0.4V
−20 µA
LOW Level Output Voltage Applied VIH = Min, VIL = Max
I
OS
Short Circuit Output Current VCC = Max (Note 3) −20 −100 mA
I
CCH
Supply Current with Outputs HIGH VCC = Max (Note 4) 5.9 10 mA
I
CCL
Supply Current with Outputs LOW VCC = Max (Note 4) 9.2 16 mA
I
CCZ
Supply Current with Outputs Disabled VCC = Max (Note 4) 12 19 mA
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