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DesigningforLoadTransients
PTN78000A
SLTS246A–APRIL2005–REVISEDMAY2005
thetransientresponseofthedc/dcconverterhasbeencharacterizedusingaloadtransientwithadi/dtof
1a/µs.thetypicalvoltagedeviationforthisloadtransientisgiveninthedatasheetspecificationtableusingthe
requiredvalueofoutputcapacitance.asthedi/dtofatransientisincreased,theresponseofaconverter's
regulationcircuitultimatelydependsonitsoutputcapacitordecouplingnetwork.thisisaninherentlimitationof
anydc/dcconverteroncethespeedofthetransientexceedsitsbandwidthcapability.ifthetargetapplication
specifiesahigherdi/dtorlowervoltagedeviation,therequirementcanonlybemetwithadditionaloutput
capacitordecoupling.inthesecases,specialattentionmustbepaidtothetype,值,andesrofthe
capacitorsselected.
ifthetransientperformancerequirementsexceedthosespecifiedinthedatasheet,theselectionofoutput
capacitorsbecomesmoreimportant.reviewtheminimumesrinthecharacteristicdatasheetfordetailsonthe
capacitancemaximum.
table3.recommendedinput/outputcapacitors
CAPACITORCHARACTERISTICSQUANTITY
85°C
capacitorvendor/
相等的
VENDOR
WORKINGMAXIMUMPHYSICAL
组件
VALUESERIESINPUTOUTPUT
号码
VOLTAGERIPPLESIZE
序列
(µf)resistancebusbus
(v)电流(mm)
(等效串联电阻)(
Ω
)
(i
rms
)(毫安)
fc(放射状的)351000.1175508×11,5
≥
11EEUFC1H181
fc(smd)351000.01567010×10,2
≥
1
(1)
1EEVFC1V101P
pxa16vc180mf60(v
I
,|v
O
|<
unitedchemi-conpxa(smd)161800.01643608×12
≥
1
(1)
≤
1
14v)
ps251000.02043008×10,5
≥
1
(1)
≤
110fs100m(v
I
,|v
O
|<22v)
lxz501000.2204858×12,5
≥
11LXZ50VB101M8X12LL
MVY50VC101M10X10TP
mvy(smd)501000.30050010×10
≥
11
(|v
O
|
≤
5v)
nichiconuwg(smd)501000.30050010×10
≥
11UWG1H101MNR1GS
f550(tantalum)101000.05520007.7×4,3n/r
(1)
≤
3
(2)
f551a107mn(|v
O
|
≤
5v)
hd501200.07297910×12,5
≥
11UHD1H101MPR
sanyoos-consvp(smd)201000.02425008×12
≥
1
(1)
≤
120svp100m(v
I
,|v
O
|
≤
16v)
sp161000.032289010×5
≥
1
(1)
≤
116sp100m(v
I
,|v
O
|
≤
14v)
7,3l×4,3tpsv107m020r0085
201000.0851543n/r
(3)
≤
2
w×4,1h(|v
O
|
≤
10v)
avxtantalumtps(smd)
TPSE107M020R0200
201000.200>817n/r
(3)
≤
2
(|v
O
|
≤
10v)
GRM32ER61C476M
muratax5rceramic16470.002>100032251
(1)
≤
2
(|v
o
|~V
I
≤
13.5v)
grm422x5r476m6.3
muratax5rceramic6.3470.002>10003225n/r
(1)
≤
2
(|v
O
|
≤
5.5v)
c3225x7r1e225kt/mt
tdkx7rceramic252.20.002>1000smd
≥
4
(4)
1
(|v
O
|
≤
20v)
GRM32RR71E225K
muratax7rceramic252.20.002>10003225
≥
4
(4)
1
(|v
O
|
≤
20v)
C1210C225K3RAC
kemetx7rceramic252.20.002>10003225
≥
4
(4)
1
(|v
O
|
≤
20v)
12103C225KAT2A
avxx7rceramic252.20.002>10003225
≥
4
(4)
1
(|v
O
|
≤
20v)
muratax7rceramic504.70.002>10003225
≥
21GRM32ER71H475KA88L
tdkx7rceramic502.20.002>1000
≥
41C3225X7R1H225KT
murataradialthrough-hole502.20.004>1000
≥
41RPER71H2R2KK6F03
(1)thevoltageratingoftheinputcapacitormustbeselectedforthedesiredoperatinginputvoltagerangeoftheregulator.tooperatethe
regulatoratahigherinputvoltage,selectacapacitorwiththenexthighervoltagerating.
(2)themaximumvoltageratingofthecapacitormustbeselectedforthedesiredset-pointvoltage(v
O
).tooperateatahigheroutput
电压,selectacapacitorwithahighervoltagerating.
(3)notrecommended(n/r).thevoltageratingdoesnotmeettheminimumoperatinglimitsinmostapplications.
(4)themaximumratingoftheceramiccapacitorlimitstheregulator'soperatinginputvoltageto20v.selectaalternativeceramic
componenttooperateatahigherinputvoltage.
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