TL/F/12040
DS36C278
Low
Power
Multipoint
EIA-RS-485
Transceiver
December 1995
DS36C278
Low Power Multipoint EIA-RS-485 Transceiver
General Description
The DS36C278 is a low power differential bus/line trans-
ceiver designed to meet the requirements of RS-485 stan-
dard for multipoint data transmission. In addition it is com-
patible with TIA/EIA-422-B.
The CMOS design offers significant power savings over its
bipolar and ALS counterparts without sacrificing ruggedness
against ESD damage. The device is ideal for use in battery
powered or power conscious applications. I
CC
is specified at
500
m
A maximum.
The driver and receiver outputs feature TRI-STATE
É
capa-
bility. The driver outputs operate over the entire common
mode range of
b
7V to
a
12V. Bus contention or fault situa-
tions that cause excessive power dissipation within the de-
vice are handled by a thermal shutdown circuit, which forces
the driver outputs into the high impedance state.
The receiver incorporates a fail safe circuit which guaran-
tees a high output state when the inputs are left open.
²
The DS36C278T is fully specified over the industrial temper-
ature range (
b
40
§
C to
a
85
§
C).
Features
Y
100% RS-485 compliant
Ð Guaranteed RS-485 device interoperation
Y
Low power CMOS design
I
CC
500
m
A max
Y
Built-in power up/down glitch-free circuitry
Ð Permits live transceiver insertion/displacement
Y
DIP and SOIC packages available
Y
Industrial temperature range
b
40
§
C to
a
85
§
C
Y
On-board thermal shutdown circuitry
Ð Prevents damage to the device in the event of ex-
cessive power dissipation
Y
Wide common mode range
b
7V to
a
12V
Y
Receiver open input fail-safe
²
Y
(/4
unit load (DS36C278)
t
128 nodes
Y
(/2
unit load (DS36C278T)
t
64 nodes
Y
ESD (human body model)
t
2 kV
Y
Drop in replacement for:
Ð LTC485, MAX485, DS75176, DS3695
Connection and Logic Diagram
TL/F/12040 – 1
Order Number DS36C278TM, DS36C278TN,
DS36C278M, DS36C278N
See NS Package Number M08A or N08E
Truth Table
DRIVER SECTION
RE
*
DE
DI
DO/RI
DO
*
/RI
*
X
H
H
H
L
X
H
L
L
H
X
L
X
Z
Z
RECEIVER SECTION
RE
*
DE
RI-RI
*
RO
L
L
t
a
0.2V
H
L
L
s
b
0.2V
L
H
L
X
Z
L
L
OPEN
²
H
²
Note:
Non-terminated, open input only
TRI-STATE
É
is a registered trademark of National Semiconductor Corporation.
C
1996 National Semiconductor Corporation
RRD-B30M36/Printed in U. S. A.
http://www.national.com
Summary of Contents for DS36C278 s and
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