SA60

SA60U

5

P r o d u c t I n n o v a t i o n F r o m

®

PWM INPUT-IstheTTLcompatibledigitalinputforcontrollingthePWMpulsewidthofthebridge.Adutycycle

greaterthan50%willproducegreaterthan50%dutycyclepulsesoutoftheAout.Adutycyclelessthan50%

willproducegreaterthan50%dutycyclefromtheBout.Foranaloginputs,theintegrationcapacitorforthe

internalclockmustbeconnectedbetweenthispinandanalogground.Theinternalswitchingfrequencyispro-

grammableupto125kHzbyselectionoftheintegrationcapacitor.Theformulais:

BYPASSING

Adequatebypassingofthepowersuppliesisrequiredforproperoperation.Failuretodosocancauseerraticand

lowefficiencyoperationaswellasexcessiveringingattheoutputs.TheVssupplyshouldbebypassedwithat

leasta1µFceramiccapacitorinparallelwithanotherlowESRcapacitorofatleast10µFperampofoutputcurrent.

Capacitortypesratedforswitchingapplicationsaretheonlytypesthatshouldbeconsidered.The1µFceramic

capacitormustbephysicallyconnecteddirectlytotheVsandPOWERGNDpins.Evenoneinchofleadlengthwill

causeexcessiveringingattheoutputs.Thisisduetotheveryfastswitchingtimesandtheinductanceofthelead

connection.ThebypassingrequirementsoftheVccsupplyarelessstringent,butstillnecessary.A.1µFto.47µF

ceramiccapacitorconnecteddirectlytotheVccandANALOGGNDpinswillsuffice.

PCB LAYOUT

ThedesignerneedstoappreciatethattheSA60combinesinonecircuitbothhighspeedhighpowerswitchingand

lowlevelanalogsignals.Certainlayoutrulesofthumbmustbeconsideredwhenacircuitboardlayoutisdesigned

usingtheSA60:

1. Bypassingofthepowersuppliesiscritical.Capacitorsmustbeconnecteddirectlytothepowersupplypinswith

veryshortleadlengths(wellunder1inch).Ceramicchipcapacitorsarebest.

2. ConnectANALOGGNDtoPOWERGNDwithaconductorhavingnointermediateconnections.ConnectallVs

powersupply,filterandloadrelatedgroundconnectionstoPOWERGNDkeepingtheseconductorsseparate

untilreachingpin6.ConnectallVccpowersupplyandinputsignalrelatedgroundconnectionstoANALOG

GNDkeepingconductorsseparateuntilreachingpin1.Donotallowgroundloopstoformbymakingadditional

groundconnectionsatthelowsideofthephysicalpowersupplies.Ifgroundplaneisuseddonotallowmore

than1mAtoflowthroughit.

3. Bewareofcapacitivecouplingbetweenoutputconnectionsandsignalinputsthroughtheparasiticcapacitance

betweenlayersinmultilayerPCBdesigns.

4. Donotrunsmallsignaltracesbetweenthepinsoftheoutputsection(pins8-12).

CURRENT SENSE

Therearetwoloadcurrentsensingpins,ISENSEAandISENSEB.ThetwopinscanbeshortedtoPOWERGND

inthevoltagemodeconnectionbutbothmustbeusedinthecurrentmodeconnection.ItisrecommendedthatR

SENSEresistorsbenon-inductive.LoadcurrentflowsintheISENSEpins.TheSA60hasnointernalcurrentlimit.

TRANSIENT SUPPRESSION

AnRCnetworkofa100pFCapacitorandaoneohmresistorisrequiredasshownintheexternalconnectiondia-

gramonpage1.Thisnetworkassuresproperoperationundervariousloads.Minimalpowerisdissipatedinthe

resistor.

– 50

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