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100%DutyCycleLowDropoutOperation
V
在(最小值)
V
输出(最大值)
I
输出(最大值)
R
ds(在)最大值
R
L
(7)
使能
UndervoltageLockout
ForcedPWMMode
bq25010
bq25011
bq25012
SLUS615–DECEMBER2004
thebqhybridoffersalowinput-至-outputvoltagedifferencewhilestillmaintainingoperationwiththeuseofthe
100%dutycyclemode.inthismodethep-channelswitchisconstantlyturnedon.thisisparticularlyusefulin
电池-poweredapplicationstoachievelongestoperationtimebytakingfulladvantageofthewholebattery
voltagerange.theminimuminputvoltagetomaintainregulationdependsontheloadcurrentandoutputvoltage
andcanbecalculatedas:
在哪里
I
输出(最大值)
=maximumoutputcurrentplusindicatorripplecurrent
R
ds(在)最大值
=maximump-channelswitchr
ds(在)
R
L
=DCresistanceoftheinductor
V
输出(最大值)
=nominaloutputvoltageplusmaximumoutputvoltagetolerance
pullingtheenablepin(en)lowforcesthedc-dcconverterintoshutdownmode,withashutdownquiescent
currentoftypically0.1µa.inthismodethep-channelswitchandn-channelrectifierareturnedoff,theinternal
resistorfeedbackdividerisdisconnected,andtheconverterentersshutdownmode.ifanoutputvoltage,这个
couldbeanexternalvoltagesourceorasupercapacitor,ispresentduringshutdown,thereverseleakage
currentisspecifiedunderelectricalcharacteristics.forproperoperationtheenpinmustbeterminatedand
shouldnotbeleftfloating.
pullingtheenpinhighstartsupthedc-dcconverterwiththesoft-startaspreviouslydescribed.
TheundervoltagelockoutcircuitpreventstheconverterfromturningontheswitchorrectifierMOSFETatlow
inputvoltagesorunderundefinedconditions.
thefpwminputpinallowsthehostsystemtooverridethepowersavemodebydrivingthefpwmpinhigh.在
thisstate,thedc-dcconverterremainsinthepwmmodeofoperationwithcontinuouscurrentconduction
regardlessoftheloadconditions.tyingthefpwmpinlowallowsthedevicetoenterpowersavemode
automaticallyaspreviouslydescribed.
14
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