2024年3月31日发(作者：)

ApplicationReport

SLUA456–March2008

SingleCellGasGaugeCircuitDesign

MichaelVegaandMingYuBatteryManagement

ABSTRACT

Componentsincludedinsingle-cellgasgaugecircuitdesignsareexplainedinthis

analysisandsuggestedtradeoffsareprovided,where

appropriate.

1

2

3

4

5

Introduction

..........................................................................................

High-CurrentPath

..................................................................................

GasGaugeCircuit

..................................................................................

CurrentandVoltageProtection

...................................................................

ReferenceDesignSchematic

.....................................................................

ListofFigures

Contents

1

1

3

5

5

1

2

3

4

ProtectionFETs

.....................................................................................

SenseResistor

......................................................................................

DifferentialFilter

....................................................................................

ESDProtectionforCommunicationUsingZenerDiodes

.....................................

2

3

3

4

1Introduction

TheSingle-CellGasGaugecircuithasapproximately15-20componentsinthereferencedesignfora

1-thermistor,rity,thesechipsetsaregroupedintothefollowingclassifications:

High-CurrentPath,GasGaugeCircuit,CurrentandVoltageProtection.

Thediscuete

schematicisavailableonthelastpageofthisdocument.

2High-CurrentPath

Thehigh-currentpathbeginsatthePACK+gecurrenttravelsthrough

thepack,itfindsitswaythroughthelithium-ioncellandcellconnections,thesenseresistor,protection

FETsandthenreturnstothePACK–terminal(seethereferencedesignschematicattheendofthis

document).Inaddition,somecomponentsareplacedacrossthePACK+andPACK–terminalstoreduce

effectsfromelectrostaticdischarge.

2.1ProtectionFETs

TheN-chrtable

batteryapplicationsareagoodmatchfortheSi6926ADQorequivalent.

TheVishaySi6926ADQispackagedwithtwo4.1-A,20-VdeviceswithRds(on)of33mΩwhenthegate

drivevoltageis3V.

ImpedanceTrackisatrademarkofTexasInstruments.

SLUA456–March2008

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SingleCellGasGaugeCircuitDesign1

High-CurrentPath

oftwodevicesensures

rtohavegoodESDprotection,thecoppertrace

inductanthatthe

voltageratingofbothC2andC3areadequatetoholdofftheappliedvoltageifoneofthecapacitors

becomesshorted.

R1

0.01W

4

2

3

Q4:A

SI6926ADQ

1

8

5

6

7

Q4:B

SI6926ADQ

C2

0.1mF

C3

0.1mF

tionFETs

2.2Lithium-IonCellConnections

Theimportantthingtorememberaboutthecellconnectionsisthathighcurrentflowsthroughthetopand

bottomconnections,andthereforethevoltagesenseleadsatthesepointsmustbemadewithaKelvin

ccriticalforgauging

accuracyintheImpedanceTrack™gauges.

2.3SenseResistor

Aswiththecellconnections,y

thesenselines,butthesingle-pointconnectiontothelow-currentgroundsystemmustbemadehereina

carefulmanner.

Thesenseresistorshouldhaveatemperaturecoefficientnogreaterthan100ppminordertominimize

seresistorvalueshouldbesizedtoaccurately

inteimum

sense-resistorvoltagethatcanbemeasuredaccuratelybythecoulombcounteris±igner

shouldensurethatthevo

oftenthepowerdissipationintheresistoratmaximumloadcurrentsthatsetsthemaximumacceptable

sense-resistorvalue,particularlywhenspaceconsiderationsrestrictthemaximumsizeallowableforthe

sicalsize,powerdissipation,andinsertionloss(voltagedrop)considerationsofthesense

stobebalancedagainst

theaccuracyrequirementsatlowcurrents(slightlyabovetheSLEEPthreshold),wherethesense-resistor

voltageatminimumloadcurrentsmightnotbemuchlargerthanthemeasurementoffseterrorifthe

ngle-cellapplication,10mΩisgenerallyideal.

2SingleCellGasGaugeCircuitDesignSLUA456–March2008

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