三项无刷驱动器L6235 THREE PHASE BRUSHLESS DC MOTOR DRIVER

1/39AN1625APPLICATIONNOTEOctober20031INTRODUCTIONForsmall-motorapplicationsmanyappliancedesignersfavormodernthreephasebrushlessDCmotorsbe-causeofthehighefficiency(asgreatas95%)andsmallsizeforagivendeliveredpower.Designershavetohandlecontrollogic,torqueandspeedcontrol,power-deliveryissuesandensuresafeoperationineveryloadcondition.TheL6235isahighlyintegrated,mixed-signalpowerICthatallowstoeasilydesignacompletemotorcontrolsystemforBLDCmotor.Figure1showstheL6235blockdiagram.TheICintegratessixPowerDMOS,acentralizedlogiccircuittodecodehalleffectsensorsandaconstanttOFFPWMcurrentcontroltechnique(Syn-chronousmode)plusotheraddedfeaturesforsafeoperationandflexibility.Figure1.L6235BlockDiagram.CHARGEPUMPVOLTAGEREGULATORHALL-EFFECTSENSORSDECODINGLOGICTHERMALPROTECTIONTACHOMONOSTABLEOCD1OCDOCDOCD210V5VVCPVSAGATELOGICVBOOTVBOOTOUT1OUT2SENSEAVSBOUT3SENSEBDIAGENFWD/REVBRAKEH3H1RCPULSED99IN1095BTACHORCOFFH2OCD3ONESHOTMONOSTABLEMASKINGTIMEVBOOTOCD110VVBOOTOCD210VVBOOTOCD310VSENSECOMPARATOR+-PWMVREFbyVincenzoMaranoL6235THREEPHASEBRUSHLESSDCMOTORDRIVERModernmotioncontrolapplicationsneedmoreflexibilitythatcanbeaddressedonlywithspecializedICsproducts.TheL6235isafullyintegratedmotordriverICspecificallydevelopedtodriveawiderangeofBLDCmotorswithHalleffectsensors.ThisICisaone-chipcosteffectivesolutionthatincludesseveraluniquecircuitdesignfeatures.Thesefeatures,includingauniversaldecodinglogicthatallowsthedevicetobeusedwithmostcommonHalleffectspacing,willbedescribed.Theprincipalaimofthisdevelopmentprojectwastoproduceaneasytouse,fullyprotectedpowerIC.InadditionseveralkeyfunctionsasprotectioncircuitandhighspeedPWMcurrentcontrolallowtodrasticallyreducetheexternalcomponentscounttomeetrequirementsformanydifferentapplications.AN1625APPLICATIONNOTE2/39TableofContents1INTRODUCTION................................................................................................................................12DESIGNINGANAPPLICATIONWITHL6235...................................................................................32.1CurrentRatings........................................................................................................................32.2VoltageRatingsandOperatingRange....................................................................................32.3ChoosingtheBulkCapacitor....................................................................................................52.4LayoutConsiderations.............................................................................................................52.5SensingResistor......................................................................................................................72.6Chargepumpexternalcomponents.........................................................................................82.7SharingtheChargePumpCircuitry.........................................................................................92.8ReferenceVoltageforPWMCurrentControl.........................................................................102.9InputLogicpins......................................................................................................................112.10DIAGpin.................................................................................................................................112.11Programmableoff-timeMonostable.......................................................................................122.11.1Off-timeSelectionandminimumon-time........................................................................142.11.2SlowDecayMode...........................................................................................................142.12OverCurrentDetection.........................................................................................................162.13PowerManagement...............................................................................................................202.13.1Maximumoutputcurrentvs.selectabledevices..............................................................202.13.2PowerDissipationFormulae...........................................................................................212.14Thedecodinglogic................................................................................................................242.15TachoOutputandSpeedLoop.............................................................................................252.15.1Staticperformance-SpeedRegulationvs.ResistantTorque:.......................................282.15.2Dynamicperformance:....................................................................................................292.15.3LoopStability:..................................................................................................................302.15.4Referencevoltageripple:................................................................................................302.16Brake..........................................................................