Technical Reference Note

Rev. 04.25.11

SIL/SMT80C2

8 of 20

Embedded Power for

Business-Critical Continuity

Output Capacitance

TheSIL/SMT80C2hasoutputcapacitorsinsidetheconverter.Nooutputcapacitanceisrequiredfor

stableoperation.Whenpoweringloadswithlargedynamiccurrentrequirements,improvedvoltage

regulationisobtainedbyinsertinglowESRcapacitorsascloseaspossibletotheload.LowESR

ceramiccapacitorswillhandletheshortdurationhighfrequencycomponentsofthedynamiccurrent

requirement.Inaddition,highervaluesofelectrolyticcapacitorsshouldbeusedtohandlethemid-

frequency components.

Itisequallyimportanttousegooddesignpracticeswhenconfiguringthedcdistributionsystem.Low

resistanceandlowinductancePCBlayouttracesshouldbeutilized,particularlyinthehighcurrentoutput

section.RememberthatthecapacitanceofthedistributionsystemandtheassociatedESRarewithinthe

feedbackloopofthepowercapabilities,thusaffectingthestabilityanddynamicresponseofthemodule.

Notethatthemaximumratedvalueofoutputcapacitancevariesbetweenmodelsandforeachoutput

voltagesetpoint.Astabilityvs.LoadCapacitancecalculator,(seeyoursalesrepresentative),detailshow

anexternalloadcapacitanceinfluencesthegainandphasemarginsoftheSIL/SMT80C2.

SMT Reflow Guidelines

ForaSnPbprocess:Padsshouldbeabove183C(liquidus)for90secondsmax(60-75secondstypical)

withapeaktemperatureof225C.ForaleadfreeSAC305process:padsshouldbeabove217C(liquidus)

for90secondsmax(60-75secondstypical)withapeaktemperatureof250C.

Water Washing

Not recommended.

Application(cont'd)