PKS604YSLASHF datasheet(12/24 Pages) FERYSTER

12 / 24 page

PKS603-607

Rev. I 02/07

Thermal Considerations

For the P package, the four SOURCE pins are internally

connectedtotheICleadframeandprovidethemainpathto

removeheatfromthedevice.Therefore,alltheSOURCEpins

shouldbeconnectedtoacopperareaunderneaththePeakSwitch

toactnotonlyasasinglepointground,butalsoasaheatsink.

Asthisareaisconnectedtothequietsourcenode,itshouldbe

maximizedforgoodheatsinking.Similarly,foraxialoutput

diodes,maximizethePCBareaconnectedtothecathode.

Y-Capacitor

TheplacementoftheY-typecapshouldbedirectlyfromthe

primaryinputfiltercapacitorpositiveterminaltothecommon/

return terminal of the transformer secondary.If a second

Y-typecapisrequiredfromprimarytosecondaryreturn,connect

theprimarysidedirectlytothenegativeterminaloftheinput

capacitor.Suchaplacementwillroutehighmagnitudecommon

modesurgecurrentsawayfromthePeakSwitchdevice.Note

–ifaninputπ(C,L,C)EMIfilterisused,thentheinductorin

thefiltershouldbeplacedbetweenthenegativeterminalson

theinputfiltercapacitors.

Optocoupler

PlacetheoptocouplerphysicallyclosetothePeakSwitchto

minimizetheprimarysidetracelengths.Keepthehighcurrent

highvoltagedrainandclamptracesawayfromtheoptocoupler

topreventnoisepickup.

Output Diode

For best performance, the area of the loop connecting the

secondary winding, the output diode and the output filter

capacitorshouldbeminimized.Inaddition,sufficientcopper

areashouldbeprovidedattheanodeandcathodeterminal

ofthediodeforheatsinking.Alargerareaispreferredatthe

quitecathodeterminal.Alargeanodeareacanincreasehigh

frequencyradiatedEMI.

Quick Design Checklist

As with any power supply design, all PeakSwitch designs

shouldbeverifiedonthebenchtomakesurethatcomponent

specificationsarenotexceededunderworstcaseconditions.The

followingminimumsetoftestsisstronglyrecommended:

1.Maximumdrainvoltage–VerifythattheV

DSdoesnotexceed

650Vathighestinputvoltageandpeak(overload)output

power.The50Vmargintothe700VBV

DSSspecification

allowsmarginfordesignvariation.

2.Maximumdraincurrents–Verifythesimultaneousdrain

voltageandcurrentlevelsarewithinthecurveprovidedin

Figure29underworstcaseconditions.Typicallythisoccurs

atstartup(andduringanoutputshortcircuit),highestinput

linevoltageandmaximumambienttemperature.When

makingthismeasurementusingacurrentprobe,tomonitor

thedraincurrent,ensuretheresultsarecorrectedforthe

10-20nscurrentprobedelay.

3.Maximumdraincurrent–Atmaximumambienttemperature,

maximuminputvoltageandpeakoutput(overload)power,

verifydraincurrentwaveformsshownosignsoftransformer

saturation.Ifthetransformershowssignsofsaturation,

it should be redesigned with a lower flux density, or a

higherqualitycorematerialshouldbeused.Toprevent

false triggering of the current limit, verify the leading

edgecurrentspikeeventisbelowI

INIT(MIN)attheendofthe

LEB(MIN).Underallconditions,themaximumdraincurrent

shouldbebelowtheabsolutemaximumlimitspecifiedin

theAbsoluteMaximumRatingssection.

4.ThermalCheck–At specifiedmaximumoutputpower,

minimuminputvoltageandmaximumambienttemperature,

verifythatthetemperaturespecificationsarenotexceededfor

PeakSwitch

,transformer,outputdiodeandoutputcapacitors.

Enoughthermalmarginshouldbeallowedforpart-to-part

variationoftheR

DS(ON)ofPeakSwitchasspecifiedinthe

datasheet.Underlowline,maximumpower,amaximum

PeakSwitch

SOURCEpinortabtemperatureof110°Cis

recommendedtoallowforthesevariations.

Design Tools

Up-to-dateinformationondesigntoolscanbefoundatthe

PowerIntegrationswebsite:www.powerint.com.

PKS604Y/F Datasheet(PDF) 12 Page - FERYSTER Inductive Components Manufacturer

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