TPS40200-EP中文资料(14)

元器件交易网

SGLS371–JANUARY2007

GENERALINFORMATION(continued)

MOSFETGateDrive

Theoutputdriversinkingcurrentisapproximately200mAandisdesignedtodriveP-channelpowerFETs.WhenthedriverpullsthegatechargeoftheFET,itiscontrollingto–8V,thedrivecurrentfoldsbacktoalowlevelsothathighpowerdissipationonlyoccursduringtheturnonperiodoftheFET.ThisfeatureisparticularlyvaluablewhenturningonaFETathighinputvoltages,whereleavingthegatedrivecurrentonwouldotherwisecauseunacceptablepowerdissipation.

UndervoltageLockout(UVLO)Protection

UVLOprotectionensuresproperstartupofthedeviceonlywhentheinputvoltagehasexceededminimumoperatingvoltage.Undervoltageprotectionincorporateshysteresis,whicheliminateshiccupstartingincaseswhereinputsupplyimpedanceishigh.

Figure28.UndervoltageLockout

Undervoltageprotectionensuresproperstartupofthedeviceonlywhentheinputvoltagehasexceededminimumoperatingvoltage.TheUVLOlevelismeasuredattheVDDpinwithrespecttoGND.Startupvoltageistypically4.3V,withapproximately200mVofhysteresis.Thepartshutsoffatanominal4.1V.AsshowninFigure28whentheinputVDDvoltagerisesto4.3V,the1.3-Vcomparator’sthresholdvoltageisexceededandoccurs.Feedbackfromtheoutputclosestheswitchandshuntsthe200-k resistorsothatanapproximate200-mVlowervoltage,or4.1V,isrequiredbeforethepartshutsdown.

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