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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP1481E-1485E_102_102710
6
AlogicLOWonRE(pin2)willenablethe
receiver,alogicHIGHonRE(pin2)willdis-
ablethereceiver.
ThereceiverfortheSP1481EandSP1485E
willoperateuptoatleast20Mbps.Thereceiver
foreachofthetwodevicesisequippedwiththe
fail-safefeature.Fail-safeguaranteesthatthe
receiveroutputwillbeinaHIGHstatewhen
theinputisleftunconnected.
Shutdown Mode
SP1481E
TheSP1481EisequippedwithaShutdown
mode.ToenabletheShutdownstate,both
the driver and receiver must be disabled
simultaneously.
AlogicLOWonDE(pin3)andalogicHIGH
onRE(pin2)willputtheSP1481EintoShut-
downmode.InShutdown,supplycurrentwill
droptotypically1μA.
ESD TOLERANCE
The SP1481E Family incorporates rug-
gedizedESDcellsonalldriveroutputand
receiver input pins. The ESD structure is
improvedoverourpreviousfamilyformore
rugged applications and environments
sensitive to electro-static discharges and
associatedtransients.TheimprovedESD
toleranceisatleast±15kVwithoutdamage
norlatch-up.
TherearedifferentmethodsofESDtesting
applied:
a)MIL-STD-883,Method3015.7
b)IEC1000-4-2Air-Discharge
c)IEC1000-4-2DirectContact
The Human Body Model has been the
generally accepted ESD testing method
for semiconductors. This method is also
specied in MIL-STD-883, Method 3015.7
for ESD testing. The premise of this ESD
testistosimulatethehumanbody’spotential
tostoreelectro-staticenergyanddischarge
ittoanintegratedcircuit.Thesimulationis
performedbyusingatestmodelasshown
inFigure7.ThismethodwilltesttheIC’s
capabilitytowithstandanESDtransientdur-
ingnormalhandlingsuchasinmanufactur-
ingareaswheretheICstendtobehandled
frequently.
DESCRIPTION
TheSP1481EandSP1485Earehalf-duplex
differentialtransceiversthatmeettherequire-
mentsofRS-485andRS-422.Fabricated
with a Exar proprietary BiCMOS process,
theseproductsrequireafractionofthepower
ofolderbipolardesigns.
TheRS-485standardisidealformulti-drop
applicationsandforlong-distanceinterfaces.
RS-485allowsupto32driversand32receiv-
erstobeconnectedtoadatabus,makingit
anidealchoiceformulti-dropapplications.
Sincethecablingcanbeaslongas4,000
feet,RS-485transceiversareequippedwith
awide(-7Vto+12V)commonmoderange
to accommodate ground potential differ-
ences. Because RS-485 is a differential
interface,dataisvirtuallyimmunetonoise
inthetransmissionline.
Drivers
The driver outputs of the SP1481E and
SP1485Earedifferentialoutputsmeetingthe
RS-485andRS-422standards.Thetypical
voltageoutputswingwithnoloadwillbe0
Voltsto+5Volts.Withworstcaseloading
of54Ωacrossthedifferentialoutputs,the
driverscanmaintaingreaterthan1.5Vvolt-
agelevels.ThedriversoftheSP1481E,and
SP1485Ehaveanenablecontrollinewhich
isactiveHIGH.AlogicHIGHonDE(pin3)
willenablethedifferentialdriveroutputs.A
logic LOW on DE (pin 3) will tri-state the
driveroutputs.
The transmitters of the SP1481E and
SP1485E will operate up to at least
20Mbps.
Receivers
TheSP1481EandSP1485Ereceivershave
differential inputs with an input sensitivity
aslowas±200mV.Inputimpedanceofthe
receiversistypically15kΩ(12kΩminimum).
Awidecommonmoderangeof-7Vto+12V
allowsforlargegroundpotentialdifferences
between systems. The receivers of the
SP1481E and SP1485E have a tri-state
enablecontrolpin.