National DS36C278 User Manual
General description, Features, Connection and logic diagram
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 mA maximum
The driver and receiver outputs feature TRI-STATE
capa-
bility The driver outputs operate over the entire common
mode range of b7V to a12V 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
The DS36C278T is fully specified over the industrial temper-
ature range (b40 C to a85 C)
Features
Y
100% RS-485 compliant
Guaranteed RS-485 device interoperation
Y
Low power CMOS design
I
CC
500 mA max
Y
Built-in power up down glitch-free circuitry
Permits live transceiver insertion displacement
Y
DIP and SOIC packages available
Y
Industrial temperature range
b
40 C to a85 C
Y
On-board thermal shutdown circuitry
Prevents damage to the device in the event of ex-
cessive power dissipation
Y
Wide common mode range
b
7V to a12V
Y
Receiver open input fail-safe
Y
unit load (DS36C278)
t
128 nodes
Y
unit load (DS36C278T)
t
64 nodes
Y
ESD (human body model)
t
2 kV
Y
Drop in replacement for
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
H
Note
Non-terminated open input only
TRI-STATE
is a registered trademark of National Semiconductor Corporation
C1996 National Semiconductor Corporation
RRD-B30M36 Printed in U S A
http
www national com