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UDG−03041
+
SCL
PACK−
PACK+
静电释放 保护
D1
5.6 v
SDA
静电释放 保护
D2
5.6 v
R7
100
Ω
R8
100
Ω
R1
1 k
Ω
C1
0.1
µ
F
R2
1 k
Ω
R
S
0.02
Ω
R4
10 k
Ω
C2
0.1
µ
F
C3
0.1
µ
F
C4
0.1
µ
F
C3
0.1
µ
F
R3
1 k
Ω
R5
100
Ω
R6
100
Ω
li-ion protector
li-ion
或者
li-pol
pgm tp
1
2
3
4
9
8
7
6
GPIO
SRP
SRN
BAT
RBI
VCC
VSS
SCL
bq27200DRK
5 SDA
10PGM
11
度量
ChargeandDischargeCoulometricandCurrentMeasurements
bq27000,bq27200
SLUS556B–SEPTEMBER2004–REVISEDNOVEMBER2004
functionaldescription(持续)
figure3showsatypicalapplicationcircuit.differentialsenseofthevoltageacrossthecurrentsenseresistor,
R
S
,improvesdeviceperformance,leadingtoanimprovementinreportedtime-至-emptyaccuracy.aninternal,3
µapull-downonthehdqorsdaandscllinesensuresthatthedevicedetectsalogic
0
onthecommunication
linesandallowsthedevicetoautomaticallyenterthelow-powersleepmodewhenthesystempowerisswitched
offorthepackisremoved.a100k
Ω
pulluptoV
CC
canbeaddedtothecommunicationlinesifthisfeatureneeds
tobedisabled.thebqjuniorcanoperatedirectlyfromasingleli-ionorli-polcell.
figure3.typicalapplicationcircuit(bq27000)
asshowninthefunctionalblockdiagram,thebqjuniorusesadedicatedfullydifferentialdelta-sigmacoulomb
计数器(dscc)forchargeanddischargecurrentandcoulometricmeasurementsandananalog-至-数字的
转换器(模数转换器)forbatteryvoltageandtemperaturemeasurements.bothdsccandadcareautomatically
compensatedforoffset.nousercalibrationorcompensationisrequired.aneepromoffsetvaluecanbe
programmedtocompensateforcontributionstothedsccoffsetduetothepcblayout.
ThebqJUNIORusesaDSCCtoperformacontinuousintegrationofthevoltagewaveformacrossasmallvalue
senseresistorinthenegativeleadofthebattery,asshowninfigure3.theintegrationofthevoltageacrossthe
senseresistoristhechargeaddedorremovedfromthebattery.becausethedsccdoesadirectintegrationof
thewaveform,theshapeofthecurrentwaveformthroughthesenseresistordoesnothaveanyeffectonthe
coulometricmeasurementaccuracy.thelow-passfilterthatfeedsthesenseresistorvoltagetothebqjunior
srpandsrninputsfiltersoutsystemnoiseanddoesnotaffectthecoulometricmeasurementaccuracy,
becausethelow-passfilterdoesnotchangetheintegratedvalueofthewaveform.thebqjunioralsousesthe
dscctomeasurecurrent.thereportedcurrentisdeterminedbytheaveragevoltageacrossthesenseresistor
overa5.12secondinterval.
8
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