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零件编号 | 54LS138 | ||
描述 | (54LS138 / 54LS139) Decoders/Demultiplexers | ||
制造商 | National Semiconductor | ||
LOGO | |||
1 Page
( DataSheet : www.DataSheet4U.com )
June 1989
54LS138 DM54LS138 DM74LS138
54LS139 DM54LS139 DM74LS139
Decoders Demultiplexers
General Description
These Schottky-clamped circuits are designed to be used in
high-performance memory-decoding or data-routing appli-
cations requiring very short propagation delay times In
high-performance memory systems these decoders can be
used to minimize the effects of system decoding When
used with high-speed memories the delay times of these
decoders are usually less than the typical access time of the
memory This means that the effective system delay intro-
duced by the decoder is negligible
The LS138 decodes one-of-eight lines based upon the con-
ditions at the three binary select inputs and the three enable
inputs Two active-low and one active-high enable inputs
reduce the need for external gates or inverters when ex-
panding A 24-line decoder can be implemented with no ex-
ternal inverters and a 32-line decoder requires only one
inverter An enable input can be used as a data input for
demultiplexing applications
The LS139 comprises two separate two-line-to-four-line de-
coders in a single package The active-low enable input can
be used as a data line in demultiplexing applications
All of these decoders demultiplexers feature fully buffered
inputs presenting only one normalized load to its driving
circuit All inputs are clamped with high-performance
Schottky diodes to suppress line-ringing and simplify system
design
Features
Y Designed specifically for high speed
Memory decoders
Data transmission systems
Y LS138 3-to-8-line decoders incorporates 3 enable in-
puts to simplify cascading and or data reception
Y LS139 contains two fully independent 2-to-4-line decod-
ers demultiplexers
Y Schottky clamped for high performance
Y Typical propagation delay (3 levels of logic)
LS138 21 ns
LS139 21 ns
Y Typical power dissipation
LS138 32 mW
LS139 34 mW
Y Alternate Military Aerospace devices (54LS138
54LS139) are available Contact a National Semicon-
ductor Sales Office Distributor for specifications
Connection Diagrams
Dual-in-Line Package
Dual-in-Line Package
TL F 6391 – 1
Order Number 54LS138DMQB 54LS138FMQB
54LS138LMQB DM54LS138J DM54LS138W
DM74LS138M or DM74LS138N
See NS Package Number E20A J16A
M16A N16E or W16A
C1995 National Semiconductor Corporation TL F 6391
TL F 6391 – 2
Order Number 54LS139DMQB 54LS139FMQB
54LS139LMQB DM54LS139J DM54LS139W
DM74LS139M or DM74LS139N
See NS Package Number E20A J16A
M16A N16E or W16A
RRD-B30M105 Printed in U S A
www.DataSheet4U.com
Physical Dimensions inches (millimeters) (Continued)
16-Lead Ceramic Flat Package (W)
Order Number 54LS138FMQB 54LS139FMQB DM54LS138W or DM54LS139W
NS Package Number W16A
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL
SEMICONDUCTOR CORPORATION As used herein
1 Life support devices or systems are devices or
systems which (a) are intended for surgical implant
into the body or (b) support or sustain life and whose
failure to perform when properly used in accordance
with instructions for use provided in the labeling can
be reasonably expected to result in a significant injury
to the user
2 A critical component is any component of a life
support device or system whose failure to perform can
be reasonably expected to cause the failure of the life
support device or system or to affect its safety or
effectiveness
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National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications
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页数 | 8 页 | ||
下载 | [ 54LS138.PDF 数据手册 ] |
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