SC4525C View Datasheet(PDF) - Semtech Corporation

Part Name

Description

MFG CO.

SC4525C

28V 3A Step-Down Switching Regulator

Semtech Corporation 

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SC4525C

Applications Information (Cont.)

12 =OS=)1W=_>VR=C(IN⋅I6(V4NDVC2O+⋅O=IV1O0L+DVOVI.+%⋅VD0OFVOI+FSLTralIODSVV⋅No−⋅eEWcihoICD)VgOosS⋅cV−⋅eo4D)pFu⋅Dpu(⋅RC⋅15p1LFSoErr(gsW⋅2SS1+ea1n−Ct(WAoV5c1asTIVRo−D8aNyCeE6bINF−ml)D(⋅ialb+FDooi)Cpnt)SOff)y1NdeWRTR.DDDLIDLIaRCnCDDDDtc3RRO4⋅44fh1n1oLsMMIVIIVIaIiCNL=N=sNLILedaENdm==SSOOs==eeRSOttp=_>i=_>VtAVSRRheC=pi=NcCC((DIenIo(tDCNNII6(V44o6(V4Grde1BcNNrBSDDVVniG4a52N2SOOanC)nnS++⋅⋅5g2NHTOD.pO=I=ITnV1V100vOLsLn++D2D5DoRRGCCVCCVTAACOOVVasVneVI.+Ij.+%5C%MTAu⋅⋅VVD0D0OOFKSFViV77PotctCnO5588CCOrISIeY+h+WIIitWODOSVDSVtV⋅NeVe⋅NWi−D−⋅(o⋅EoE=n(====CeWW==I==IIMbDD)n)OoVVtOOn)S)S⋅⋅tprDV−V−⋅h⋅dDD))1EFe(0F⋅D22⋅D22−−(⋅i(⋅≈RRRC1Cor⋅ro1⋅11L1sLFgFaSS0sd.EiEπe((tπππ222sWe⋅DW⋅SdioSSS1+G1+11+mn1−−s(A(WF4WA2FoA⋅g⋅8001s1Cp0rCTIT1101t6osPZ−Dt−D8D8DaeAao1o1⋅⋅⋅R2m6−02−1S)/)osDD1ll⋅⋅2⋅5npRRCcooG00R.FFωDefDh9⋅s0)C)1sggro7t71ShSPa1Sep)t⋅)o11Dtt−WWWBku01a)1,3yrMG2(ewop01d3⋅⋅.1a8i(=o1CCeoC1h3c⋅1d+Ateh⋅O22OiR⋅s+lRRtGCCC6AAsVVei222thVSe77Po.crs558CCO/V..2e11vWam13RUO⋅=ω====e===.MpTUk2⋅1Eaf⋅>nT1Spω1r(08122π2−−≈iQh1Re⋅Vn0gi0p.F01πCnπiq1π222tGg++mC−10≈aA3F2g⋅u⋅O8003CCh0C1016issZ)e3nAR=1⋅⋅⋅OR⋅260n1/ti1ll⋅21DC5=2Rnooh0G00/R.cω⋅9⋅0OggCgπe71y1.ωPVSp⋅V4−W,021F⋅)n2,3O5BMG2(8p01)31n8(=01CF13⋅1F+ATblao(StcFicg TaaaIf8⋅no22neE⋅Raoo⋅onnn+hhiuiu61sdanAeovdcs222Smnrddeitcs.k0sEleosdc/pu)e..211utk,131RbeS⋅nmdtpabωrt3)crf.daahork2⋅Rco1Eltoea⋅tcobnaRRωRRGCC⋅1CCGCCiCCAAlSiAAωoaeVVlVV P1crhπnonncuocQz2Rn⋅cy0n777Po7cPon(co55Z88CC5588CCWpkFe0g1eucoastbCnk1WV2sW:c+vhnCa−o==rn=======rp==f0==≈======3ltsMMCOcMdeo3eeeCtr⋅tvernti)sueh)o31s1a1iRrr(0(0Re222222−−22−−=≈(≈vOaLFp1l⋅1t2ttnrlmenrvggo0f0r0.o.1oCeeπsE1gπrZ=2 πoπππuππ2222220tto/(G,sG⋅Se+mw+m111rr−oeroaCvAOAF2FF2πF⋅l⋅⋅nRf⋅oo1800800.loωtn6VCaC0e0CCe1a1V1w1t401tpro0616-CsPdsZPZ5ec,fuA2AuFam⋅fts,11n1mr12⋅⋅O⋅⋅⋅R⋅Rl560⋅6r0Brut1Oi1//8tgtpRw1llat1llc⋅2⋅2)lte5a5ifRRRooR1oo3pangG0oGl00p0R.oR.phωωuo0i9,⋅eF97⋅0a0qtniggggg,7.Fcu77.17a1ounPt PlnSmSt0p3p⋅⋅hutia⋅−u−hWWeiotlp0F1ft01h))cn1o,3,3haneiMG2MrG2((pir(et00e1c133.grdo0l1,1niadVsi8f8(e(==e=rs1C1Caoa111u3piw3scS⋅1⋅13+OA+AtnvnpCnni1⋅⋅2222yr(hR)CR)an⋅⋅i+i+sωCt⋅e6a6s8sddt 522222te24ap)t2SicScfcAr.s.ssZ.se7e//i.t5..2o..21a11a1hoi2sn9e1313RRi⋅)⋅rtrfωω2=wosnn..ilannoiLdk2⋅k2⋅1En1⋅Eeht5⋅(⋅wnnssn1Cn1S1SωasuωieRRB11ππgotfiCQQRFR⋅⋅icls00ien0c4nppFiF0fl01E1DtwCCP. 11tesyihrS+h+dC−C−g1Tsfal−00≈≈a33CROtOsr33iC6fCtchnCenetCssua)o)3o3trgRlR=g=edOOrO⋅q⋅2go2⋅enhnOf.a11CCa=2d=213uss0idae0/c/⋅⋅i,fRnaiieOnOeπrπne.tn.11.s.ωωVcVn063enVpV44idstnd),,oo22F⋅F⋅nqn2o2Oi,Oel(,55BBcg88onpnGep))rruttlnnyn=o0tr0FhhFtCleit(rFFroAaneeRe1oon⋅⋅tF=od11hdsr5lcSFr=c1(piWlee00yni8.ooa8i3g,91m.1n()g33mno.v.uc5d5ootpFaωu⋅ω⋅r)R3Bpur2ei.2ilsrognZ,mZtltri22Taolp7teufi==nighhWfnut⋅e⋅rigoeeee1a1RsRttr) 00EESS11−−RR66CC⋅⋅OO1133,, ....003

EA

Vc

PWM

MODULATOR

FB

-

Vramp

COMP

SW

L1

C8

=

1Vo

2 πFP1

R7

Since the converter gain has only one dominant pole at

low frequency, a simple Type-2 compensation network

Co

R4

is sufficient for voltage loop compensation. As shown in

C5

C8

Figure 8, the voltage compensator has a low frequency

R7

Resr

R6

integrator pole, a zero at FZ1, and a high frequency pole

at FP1. The integrator is used to boost the gain at low

frequency. The zero is introduced to compensate the

excessive phase lag at the loop gain crossover due to the

Figure 7. Block diagram of control loops

integrator pole (-90deg) and the dominant pole (-90deg).

13

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