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XR79206 Datasheet, PDF (13/19 Pages) Exar Corporation – 40V, 6A Synchronous Step-Down | |||
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RON =RROONNt1O.0==N6V=VVxOIINNUfVÃTIÃÃNE([[Ã2f22ttfOO....9199NNV5.55â0OââÃ6xx[U(211((xT122.0005f..--55-11Ã1Ã000ÃÃ)E1f110f00.-8--)88))Ã]] VIN]
CFF
=
2
Ã
Ï
Ã
1
RFB1
x
5
x
fLC
XR79206
APUtorspopepgroralgiancrmaaemmtRxiOitotRnehNLnrgeIn=Msatoh=luItt1enOOtv.p0NNoOf(u6IolOV==ttuxaOCrvtgUfmPpoVVÃTeulII+tNNaatERI((dLÃÃtg2f0VDfIii.M..evoS9511oiVV5..âdVlnÃ00OOteÃ66aO[UUâ(r(g2UxxTT1CI.eLT0a5ff).-oÃÃs)1Ã0)nEE1+sfft0hffi..0-no8.)1wuÃ6nkeVâ¦IdNin)] Figure 27
RROORNNLRI==MFB=111..=00(66IOVVRxxOOFCBUUffP2ÃÃTT+ÃEERI(((L22ff0DffI..M..S995V550ââÃO.ÃÃ6[[Uâ((V22T11I..L0055)--â)11ÃÃ00))111+000--88.))1ÃÃ6kVVâ¦IINN]]
Where RFB2 has a nominal value of 2kâ¦.
(IOCP + (0.5 Ã âIL))
poPPrfrloaotgcSgerSraa,ammccatmahlcpeiRRunaLLslgcaRIIoMMitFttfeotBh==-r1setCth=aS(eCSIrORotSS.FCfrSBteIPbn-=2qSe+uoÃttRRIIwS(LLair0rDDSdIIreeMM.SS5teÃedV0rÃnO.6tcUoât1Va0Th0I.ppLe6µ)arâVA)oSc1giS++traa00nam..cn11e66dakkâ¦â¦ACsoGSfSNt-sDftraoprmtintsitmhteeo
following equation:
RRFFBBC11F==FC=RRSFFSBB2=22ÃÃÃtÏSSÃÃVV00ROO..F66UU1B1VV0TT10.6µxââVA511x fLC
FpCThehaaeelcsdfuee-lFaeotdmer-fwaCorarFgwrFindafrrCdowfCLmachFCpaFeta=pCChn=cSSaeSSic2tfuio2==otÃsorlxlittronÏSS(ÏCCwSSgÃxFFiÃÃnFâFRcg1)FieLs1B11e00rx1a00u..q66µµCmsxuVVAAOe5aiUcdtxTiotfooLnCu:steptutht ecnaepcaecsitsoarrsy.
Ï hFRieFgeFh,d-FfinroerqwcuoeannrjdcuynRcfLetpCisooi=nsletowr2ait(xnhRdFxFC)aâF1dFLd,xsCfuOngUcaTtiinonsmasrigminilarto
to a
the
frequency response. Calculate RFF from:
RFF =
1
2 x Ï x f x CFF
Where f is the switching frequency.
If RFF >0.02 x R1 then calculate RFF value from
RFF = 0.02 x R1.
Maximum Allowable Voltage Ripple at FB Pin
Note that the steady-state voltage ripple at feedback pin FB
(VFB,RIPPLE) must not exceed 50mV in order for the module
to function correctly. If VFB,RIPPLE is larger than 50mV then
COUT should be increased as necessary in order to keep
the VFB,RIPPLE below 50mV.
Where fLC, thefCCLFFCoFFRu=F==tpFu22=2tÃÃx2fÏÏÏixltÃÃexÏrâRRx11FFLf11dBBxx11oCuCxxFOb55FUlexxT-ffpLLoCCle frequency is
calculated from:
fLC =
fLCR=FF
2
=
2
x
x2
Ï
Ïx
x
xÏ
1
â 11L
âx Lf
x
xx
COUT
CCFOFUT
You must use manufacturerâs DC derating curves to
dAsheotleouralmddibnseeteptpheertfeeosfrfmteceatRRdnivFFdaeFF/no==cdra22piafaxxnclÏÏeoitcoaxx11epnffscxxsferCCaeFFcrqFFyourCreeFnsFcpycoanrnedsibnpegoantodsejVuOsttUeesTd.t
in order to get a critically damped transient load response.
In certain conditions an alternate compensation scheme
may need to be employed using ripple injection from
the inductor. An application note is being developed to
provide more information about this compensation scheme.
REV1B
13/19
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