DescriptionTheA4979isaflexiblemicrosteppingmotordriverwith built-in translator for easy operation. It is a single-chip solution, designedtooperatebipolarsteppermotorsinfull-,half-, quarter- and sixteenth-step modes, at up to 50 V and 1.5 A. The A4979 can be controlled by simple Step and Direction inputs, or through the SPI-compatible serial interface that also can be used to program many of the integrated features and to read diagnostic information.The current regulator can be programmed to operate in fixed off-time or fixed frequency PWM, with several decay modes toreduceaudiblemotornoiseandincreasestepaccuracy. In addition the phase current tables can be programmed via theserialinterfacetocreateuniquemicrostepcurrent profilestofurtherimprovemotorperformancefor specific applications.The current in each phase of the motor is controlled through a DMOS full bridge, using synchronous rectification to improve power dissipation. Internal circuits and timers prevent cross-conduction and shoot-through, when switching between high-side and low-side drives.Theoutputsareprotectedfromshortcircuits,andfeatures for low load current and stalled rotor detection are included. Chip-level protection includes: hot and cold thermal warnings, overtemperature shutdown, and undervoltage lockout.The A4979 is supplied in a 28-pin TSSOP power package with an exposed thermal pad (package type LP). This package is lead (Pb) free with 100% matte-tin leadframe plating.A4979-DS, Rev. 2Features and Benefits Typical application up to 1.5 A, 50 V Stall detect features Low RDS(on) outputs, 0.5 source and sink, typical Automatic current decay mode detection/selection Mixed, Fast, and Slow current decay modes Synchronous rectification for low power dissipation Internal UVLO and Thermal Shutdown circuitry Crossover-current protection Short circuit and open load diagnostics Hot and cold thermal warning SPI-compatible or simple Step and Direction motion control Highly configurable via SPI-compatible serial interfaceApplications Industrial stepper motor drives Printers Textile machinesMicrostepping Programmable Stepper Motor DriverWith Stall Detect and Short Circuit ProtectionPackage: 28-pin TSSOP with exposed thermal pad (suffix LP)Typical ApplicationsNot to scaleA4979Logic Supply Serial Interface Control Micro-controllerorECUOAPPGND VBBOSCOAM OBPOBM StepperMotorAGND VCP STEP DIRMS0 MS1 ENABLE RESETn SDI SDO SCK STRn VDD DIAG SENSA SENSB REF VREG CP1 CP2 Parallel Control VBB VBBLogicSupplyorECUOAPPGND VBBOSCOAM OBPOBM StepperMotorAGND VCP STEP DIRMS0 MS1 ENABLE RESETn SDI SDO SCK STRn VDD DIAG SENSA SENSB REF VREG CP1 CP2 Micro-controllerA4979 A4979Microstepping Programmable Stepper Motor DriverWith Stall Detect and Short Circuit ProtectionA49792Allegro MicroSystems, LLC115 Northeast CutoffWorcester, Massachusetts 01615-0036 U.S.A.1.508.853.5000; www.allegromicro.comSelection GuidePart Number Packing*A4979GLPTR-T 4000 pieces per reel4.4 mm 9.7 mm, 1.2 mm nominal height TSSOP with exposed thermal pad*Contact Allegro for additional packing information.Absolute Maximum Ratings With respect to GNDCharacteristic Symbol Notes Rating UnitLoad Supply Voltage VBBxApplies to VBBA and VBBB0.3 to 50 VLogic Supply Voltage VDD0.3 to 6 VPin CP1 0.3 to VBBVPins CP2, VCP 0.3 to VBB+8 VPins STEP, DIR, ENABLE, DIAG 0.3 to 6 VPin VREG 0.3 to 8.5 VPin RESETn Can be pulled to VBB with 38 k 0.3 to 6 VPin OSC 0.3 to 6 VPins MS0, MS1 0.3 to 6 VPins SDI, SDO, SCK, STRn 0.3 to 6 VPin REF 0.3 to 6 VPins OAP, OAM, OBP, OBM 0.3 to VBBVPins SENSA, SENSB 0.3 to 1 VAmbient Operating Temperature RangeTARange G; limited by power dissipation40 to 105 CMaximum Continuous Junction TemperatureTJ(max) 150 CTransient Junction Temperature TtJOvertemperature event not exceeding 10 s, lifetime duration not exceeding 10 hours, guaranteed by design and characterization175 CStorage Temperature Range Tstg 55 to 150 CThermal Characteristics may require derating at maximum conditionsCharacteristic Symbol Test Conditions* Value UnitPackage Thermal Resistance (Junction to Ambient)RJA4-layer PCB based on JEDEC standard 28 C/W2-layer PCB with 3.8 in.2 of copper area each side 32 C/WPackage Thermal Resistance (Junction to Pad)RJP2 C/W*Additional thermal information available on the Allegro website.Table of ContentsFunctional Block Diagram3Pin-out Diagram4Functional Description9Pin Functions9Driving a Stepper Motor10Diagnostics12Serial Interface Description16Phase Table Load Register17Diagnostic Registers18Application Information22Motor Movement Control 22Using the Phase Table Load Capability27Power Dissipation31Layout33Package Drawing34Appendix A. Driving a Stepper MotorA-1Microstepping Programmable Stepper Motor DriverWith Stall Detect and Short Circuit ProtectionA49793Allegro MicroSystems, LLC115 Northeast CutoffWorcester, Massachusetts 01615-0036 U.S.A.1.508.853.5000; www.allegromicro.comDMOS Full Bridge DMOS Full Bridge GateDriveChargePumpSTEPREF 6-bitDAC6-bitDACOscillator + -+ -SENSB SENSA VCPVBBAOAP OAM SENSAVBBBOBP OBM SENSBDIRRESETnENABLEVDDDIAGREF3.3VVBBVBBSDISDOSCKSTRnDACREF PWMControlBridgeControlLogicPWMControlTranslatorSerial Interface System ControlandRegistersUndervoltage, Cold Warning,Hot Warning, OvertemperatureShort Detect, Open Load Detect Stall DetectD N G P D N G ARegulatorOSC VREGPADCP2 CP1MS1MS0Functional Block DiagramMicrostepping Programmable Stepper Motor DriverWith Stall Detect and Short Circuit ProtectionA49794Allegro MicroSystems, LLC115 Northeast CutoffWorcester, Massachusetts 01615-0036 U.S.A.1.508.853.5000; www.allegromicro.comPin-out DiagramTerminal List TableName Number Description Name Number DescriptionAGND 7 Analog reference ground REF 8 Reference input voltageCP1 23 Charge pump capacitor terminal RESETn 27 Chip resetCP2 24 Charge pump capacitor terminal SCK 9 Serial data clockDIAG 16 Diagnostic output SDI 6 Serial data inputDIR 3 Direction select input SDO 17 Serial data outputENABLE 26 Bridge enable input SENSA 1 Current sense node bridge AMS0 13 Microstep select input SENSB 14 Current sense node bridge BMS1 12 Microstep select input STEP 19 Step inputOAM 25 Bridge A negative output STRn 2 Serial data strobeOAP 4 Bridge A positive output VBBA 28 Motor supply bridge AOBM 18 Bridge B negative output VBBB 15 Motor supply bridge BOBP 11 Bridge B positive output VCP 22 Above supply voltageOSC 5 Oscillator input VDD 10 Logic SupplyPAD Exposed pad for enhanced thermal dissipation; connect to groundVREG 20 Regulated voltagePGND 21 Power ground28272625242322212019181716151234567891011121314I/O & ControlTimer RegRef VDDSENSASTRnDIROAPAGNDREFVDDOBPSENSBVBBARESETnENABLEOAMVCPPGNDVREGSTEPOBMDIAGVBBB2 P C C S OSDISCKCP1MS1MS0SDOCharge Pump ELECTRICAL CHARACTERISTICS1,2 Valid at TA = 25C,VBB = 50 V, VDD = 3.3 V; unless otherwise notedCharacteristics Symbol Test Conditions Min. Typ. Max. UnitMicrostepping Programmable Stepper Motor DriverWith Stall Detect and Short Circuit ProtectionA49795Allegro MicroSystems, LLC115 Northeast CutoffWorcester, Massachusetts 01615-0036 U.S.A.1.508.853.5000; www.allegromicro.comSuppliesLoad Supply Voltage Range VBB7 50 VLoad Supply Quiescent Current IBBQENABLE = 0 4 mASleep mode, VBB = 40 V 1 10 ALogic Supply Voltage Range VDD3 5.5 VLogic Supply Quiescent Current IDDQENABLE = 0 5 mASleep mode 4 15 ACharge Pump Voltage VCPWith respect to VBB, VBB >7.5 V, ENABLE = 0, RESETn = 1 6.7 VInternal Regulator Voltage VREGENABLE = 0, RESETn = 1, VBB > 7.5 V 7.2 VInternal Regulator Dropout Voltage VREGDOENABLE = 0, RESETn = 1, VBB > 5.6 V 100 200 mVMotor Bridge OutputHigh-Side On-Resistance RONHVBB = 50 V, IOUT = 1.5 A, TJ = 25C 500 650 mVBB = 7 V, IOUT = 1.5 A, TJ = 25C 625 800 mHigh-Side Body Diode Forward VoltageVFH 1.4 VLow-Side On-Resistance RONLVBB = 50 V, IOUT = 1.5 A, TJ = 25C 500 650 mVBB = 7 V, IOUT = 1.5 A, TJ = 25C 625 800 mLow-Side Body Diode Forward VoltageVFL 1.4 VOutput Leakage Current ILOENABLE = 0, RESETn = 1, VO = VBB120 65 AENABLE = 0, RESETn = 1, VO = 0 V 200 120 AENABLE = 0, RESETn = 0, VO = VBB