SC4525DEVB View Datasheet(PDF) - Semtech Corporation

Part Name

Description

MFG CO.

SC4525DEVB

18V, 3A, 350kHz Step-Down Switching Regulator

Semtech Corporation 

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SC4525D

AC =

Applications Information (Cont.)

switching frequency. The measured minimum off time is

100ns typically. If the required duty cycle is higher than

the attainable maximum, then the output voltage will not

be abRle4

mode.

t=oRr6ea1chV.0OiVts−s1et

value

in

continuous-conduction

InductDo=r SelecVtOio+nVD

VIN + VD − VCESAT

The inductor ripple current for a non-synchronous step-

down converter in continuous-conduction mode is

RD 4IL==R6(V O1V.+0FOVSVWD− )⋅1⋅L(11 − D )

(3)

wthheeirneDdLFu1=ScW=tVaiI(NsnVc2+OtehV0+V.Oe%DV+sD−⋅wIV)OVD⋅itC(⋅c1FEShS−AWiTnDg) frequency (350kHz) and L1 is

An inductor ripple current between 20% to 50% of the

maag IfmnivatdhexoniaenmsRLgRDibIDDsn Ru144IuyeMVpLm=mfS==O=uf=_iRti=cR(Cnl(ViIvo66NeVgDO3oa nO=I5l3d1V1L+tc+5a%IOV.Vy.F⋅O0V0g%Oc,OSV+D⋅Vcu⋅VeEWDIo)iVOrSnv) −r−⋅⋅sDDRea⋅d⋅L(t111(Frnu11a⋅+iSte(n−cW1,−st8dDoI−oDO ⋅sr)v,F)DirzeSig)e1pWri.pavR⋅elwCee s-Oicadaurerrargrenaonngotgi,ndetgh, cteEhoqiemn(u4ndap)uctrihocotomnoori(ss3iees)

LcTlScIenou1hCapnre4sbruv5teapet2n3sIeDrCD5DRDLet.Dta9M.VDe1dIIeINkA=LSLOrc=_.>ci=oo=oV=VsCTu(nIpIIuNhN4(N(VDr3eVVpre2O++=.I⋅terO9OLVlh0aDm+niVIAVOn⋅+teO+%VtDFDiFVaIg+oIO⋅SVmNElDSVx−⋅n−inWWIDmVCSD)iO⋅omiVVD⋅D)nFa)Ra⋅⋅mi(⋅CC⋅Ltt⋅1SuLpuFEE⋅(+W(S1t1SiSs1o1(ma−nAh1WAf8cTTa−oe−Di−dSltn⋅)DiDCeoFnDei)nl)4Srpi)1Wvp5hue2uat⋅r5lCtavfDboOvolloeptfalottlgoahwegaeedeeri.xncttAudrraelruwnrmcesatnieoyststsr.oforrvirpeistrphiafleeyt

TrihpeplienCpLcIRI1uuNMrtS=r>_ce(Can4VIpNt2O⋅ao=D0+cf%VIitVIaOIOoND⋅b⋅rI)⋅Ou⋅sF(⋅DchS1FkWoS⋅−Wuc(1oDldn−) vbDee)rtcehro. Tshenis

to handle the

value is given

RMS

by

I RMS _ CIN = IO ⋅ D ⋅ (1 − D)

(5)

TinhpeuitnrpDipuVptOlce=avpDoaIlcLtai⋅tgaeEnScweRitm+hiun8sst⋅pFaSel1Wscoi⋅fibCceaOthioignh. Tehnisoiusgimh ptoorkteaenpt

iinnpruetdcuDacVpinOagc=ittDahIneLc⋅ecoEcnaSdnRub+ceti8eves⋅tFiESm1WMaI⋅tCefrdOomfrotmhe regulator. The

C IN > 4 ⋅ DVIION ⋅ FSW

(6)

©

2011CSeINm>te4ch⋅

CoIrOp.

DVIN ⋅

FS

W

R4

=

R

6





VO

1 .0 V

− 1 



AC =

AwC h=er−e2DD0V=⋅INlVoiIsNgt+hVGeVOCD1aA+R−llVoSVDwC⋅Ea2SbAπTlFe1CiCnpO u⋅tVVrFiOBpple voltage.

Multi-layer ceramic capacitors, which have very low ESR (a

AftXFCeho5we=rRimh−dcieeWg2Draha0)IlLmac⋅vn=lhioocdog(ltccVicaaaO2egnp+8efaFeoc⋅SVaariW6Dstpiio.n)lp⋅11yr⋅pLl(h⋅ii1u1cs1ata0a−ntfdiid−Dole3tln)eeq⋅rshui,2niagπagthe.⋅sA8RfmoM0srai⋅Snlm1lrg0icolp1ee3sprt4⋅alea2.m7pc2µipucF⋅rl1irct(e01oanµt−1ti6Fo,0an⋅µor13seFr...03

R=71=5



C5 =

15.9

AARCC2crOTCC758eah.2u==q=p==eµtuap−−0oF22icru).uπ22ieπ2LItc1ttRmo00⋅⋅81paMC016rnu⋅⋅Se=⋅a60llt_1nt2oobpo00C(⋅0trggeIVa1siN⋅ps2−O.cp01a3=G2pi0+l0tt31a8lCI%io=1esO1c3VA⋅r⋅fReD22v⋅y⋅⋅6Ido)222SO.⋅bl11..2iD(⋅t⋅1n31oFa.2⋅k⋅1Sgtp⋅1−(Whπ11ea0⋅DF011rtDC−−a)h033CVlDel3eOO⋅=)l2Eo=0⋅wSπfV1.VRi4aFt⋅2OBh58bapn0aunFFcdl⋅ok1wb0c1uo3ElnSk⋅vR2ec2eartlp⋅ee1acr0ctcri−ato6anlny⋅btc13ieec..03





C8 =

V=o1=5

Vc

expressed15a.9s

RCVVA w75ocCh====e02(r−1e.π22D1+ C⋅8001VOs⋅O6i⋅1/2sl0=Go⋅ω0t1hgPDp− W0e3)IM(LG31o=(⋅C⋅1u+1A22tRE+ps22S Sus../13RRtω⋅kcE⋅+2nS1aπQRp80FC1a+ 3C⋅OcFCs)i=St2O1Wa0/n⋅⋅.ωc4VC Ven5F2OO.B)nF

(7)

GPWM

R7 =

CGAASdt8PChCiWen=e=M=ccrr2eee−≈−faπo2C2Gts⋅Arh0e0C6IeCNesA0R⋅⋅t>l⋅hl0o(oRiEeng4g⋅Sqd1h⋅,uuG0i2Dga1c8C3Vtht1IAiIoOo⋅Ne⋅R2r6sn⋅St2.F11rw⋅S.(i13pW2⋅hω)1pπ⋅)e,10plFne10Ct−≈VhC33cRIeNOu⋅=1Ci2rs⋅orO1πeVauV2,nFt⋅tOBppt8itFu0sDtm⋅I1Lrai0pxi1n3ipmcωl⋅re2ueZ 2mav=so⋅.eR1lst0EaS1g−aR6Ces

D,

O⋅ i1s

3

.0

.3

C=5



1=5

RGCRVCCVRCCARCVVAfiiratvFU7Poc57758nn5o8C7oech58Wonrs==ds=r2ee=M=====l==de==uttu2seo1h(a21≈l0e2212o(02−Yµc2w2tugg10eg0i.tπf5πF.tπππnGtπ+m22eπho2myA+F21pV1SF2Fo⋅gC⋅0t80C⋅r1pe80csZ11u0c1o6PZ016Aus1oRece11h⋅c⋅/t⋅60i6t01⋅e1/4le1lsR2n1u5G2RoRp5Roωi0f0.G0r0.7f9⋅ωn0o9⋅ir70tuagPf77S1lp1rµPtivtW⋅gfp⋅m−etc−)kWe,0101FecM)3(3in2yM1Dr(ea0irc30131(i1Xct8y=1nn1(ap=1ib+313⋅5⋅o+pgtoca⋅a22+22Rls⋅sd⋅a+ac6ofrs.22222iprsice/wnc.tsai/..211..2Rieaoe1ω313tRω.mcoEr.rrk⋅b1kn1Er⋅Saωs⋅i1nrSidtQ1uR1omp⋅QhRo⋅p0Cic01is01poC+arsik≈t−+Os0c30dvl3O3se)anesRe3cfc)32==op⋅o2osa1Chc=2/rp=t0pn0u/iaOgωπlo1a.v1.rsωia4,4chrecun22⋅2en2af5i5r8)tpcrttpn)ttpneenoo0iFeFtoemFuFrn.r⋅nwtic1pAsdsehf0e.viifrrle1oront3eaReeuiωct⋅dlirnbitup2iZnlnderyp2ug=egclase⋅faarRied1bnuenceeE0ecgsduSd1qcet−Rrisahu6CfZriuetiae5OCg⋅hsntrUO1h3,eeest,..03 C=81=5

CGVVreda8ocPetaiWod==slMdiuen2(aec≈1gesπst+GsFhs1P3Csih1dgAARo/Rih⋅oGuωRa-7dslPnpSdWie)dd,M(1eh(ra1ae+cvvru+seeersvr/raseReωennrEnsStωeQRarsepCve+bce≈Onolrso)saRv2cigen1Ck/regiOyωn,fgin2oni)nrvwtpohualettradSgcCecu4ωuro5rrZe2rfen=5antDtRt.lsEerTpS1aahRitskCeitnesOsgea,,

GRfrvPe7eoWwg=lMtua1v≈lgag0oetGmloA2ttCC0sroAsRh⋅ionRigppSheu,retarvtiotnhlgtaangatetωhlcopeown≈ivndRepu1CrustOityo,vncoyrlcatlateigoses(.)i,.eFiωto. iZrlso=bswweRnioEteScu1RfhtiCpcinOiuagt,l

RCta7o5v=e=ru1a2sgg0eπmeA2FC0c1Zfur1erRree7wnht eraetliinnggs

diodes with somewhat higher

(thus lower forward voltages). This

C 58

==

1

22 ππFFZP11

R 77

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