National DS36C278 Home Security System User Manual


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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
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
The DS36C278T is fully specified over the industrial temper-
ature range (
b
40
Cto
a
85
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
Cto
a
85
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
a
12V
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
2kV
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
XHH H L
XHL L H
XLX Z Z
RECEIVER SECTION
RE DE RI-RI RO
LL
t
a
02V H
LL
s
b
02V L
HL X Z
L L OPEN
H
Note Non-terminated open input only
TRI-STATE
is a registeredtrademark ofNational Semiconductor Corporation
C
1996NationalSemiconductor Corporation RRD-B30M36PrintedinU SA
httpwwwnationalcom
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