Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 50-668-707 • www.exar.com

SP48E-485E_00_06609

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

specified 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

withaExarproprietaryBiCMOSprocess,

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.