DN0006 Design note A high power stepper motor driver Designs from our labs describe tested circuit designs from ST labs which provide optimized solutions for specific applications. For more information or support, visit www.st.com By Thomas Hopkins Dennis Nolan Main components L6506 Current Controller For Stepping Motors L6384E High-voltage half bridge driver Specification 2 phase bipolar motor driver Full Step, half Step and microstep operation Output current >4A* Motor voltage >50V * Circuit description When the voltage or current is outside of the capabilities of the integrated driver ICs, discrete power devices can be used with integrated gate driver ICs and a current controller to implement a high power stepper motor driver. The circuit shown in Figure 1 can easily be adapted to a wide range of current and voltage levels to meet the application requirements. The power stage is a dual full H-bridge configuration needed for a 2-phase bipolar stepper motor. Each leg of the bridge is implemented using discrete power MOS devices and an L6384E half bridge gate driver IC. The L6384E was selected for its logical compatibility with the L6506 current controller and its built-in dead time to prevent cross conduction in the bridge. The test board included a MOS device rated at 80A and 100V in a TO-220 package. By changing the power MOS devices, the design can be modified for a wide range of voltage and current. The series gate resistors may need to be changed for different power MOS devices and can be selected to set the switching time of the power MOS. The test board used power transistors in the TO-220 package that allows a very simple heat sink configuration. For moderate power levels, in the range of 5 to 10A, it’s possible to build a very compact drive using power transistors in D2PAK with just the copper area on the PCB for heat sink and the L6384ED and L6506D in SO package. * Depends on selected power MOS device. April 2012 DN0006 Rev 1 1/7 www.st.com April 2012 74HC08 3 DCP 1 4.7k R31 2 10K R11 14 DN0006 Rev 1 4 L6384 GND LVG OUT VBoot HVG 5 6 8 7 P15V 5 6 8 7 200 R6 0.22uF D4 200 C4 R5 D3 200 R3 0.22uF D2 200 C2 R2 D1 1 1 1 1 22 R20 22 R19 3 4 IN Vcc DT/DS U2 LVG OUT VBoot HVG 0.22uF C3 L6384 GND IN Vcc DT/DS P15V 2 10K 1 2 3 200 R4 4 1 2 3 U1 0.22uF C1 3 R13 PHASE2 PHASE1 200 R1 2 U9A P5V C13 680uF 3 2 1 + 2 OFFA ENA 1 2 P1 Q4 Q3 DCP Q2 Q1 DCP 2 0.1, 5W R10 2.2K R34 1.0Uf C10 2 1 P2 1.0Uf C9 D9 SENSE1 Figure 1a. Schematic diagram, page 1 3 % 1 /4 W 7 2/7 www.st.com April 2012 U9B 74HC08 6 1 1 /4 W 4.7k 2 14 DN0006 Rev 1 L6384 GND LVG OUT VBoot HVG 5 6 8 7 0.22uF 200 R14 D8 200 R12 D7 200 R9 D6 C7 C6 1 1 1 22 R22 22 R21 3 4 IN Vcc DT/DS P15V 5 0.22uF 2 10K 1 2 3 U4 LVG OUT 0.22uF C8 L6384 GND 6 8 7 1 3 R16 PHASE4 200 R17 4 VBoot HVG 200 R8 D5 2 5 4 R33 R15 IN Vcc DT/DS P15V 3 10K 1 2 3 U3 0.22uF C5 2 OFFB ENB P5V PHASE3 200 R7 Q8 Q7 DCP Q6 Q5 DCP 2 0.1, 5W R18 2 1 P3 1.0Uf C11 2.2K R35 1.0Uf C12 D10 SENSE2 Figure 1b. Schematic diagram, page 2 3 % 7 3/7 www.st.com VREFA VREFB P5V P4 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 15V April 2012 J2 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 DN0006 Rev 1 REMOVE JUMPER FOR FAST DECAY INSTALL JUMPER FOR SLOW DECAY WJ1 7 P5V 5 14 PHASE4 U8B 2 4 1 6 10K 1 % 1/4W R32 10 9 13 12 C19 2.2 nF % 1/4W U8C U8D 9 8 7 6 5 4 3 2 1 8 11 Gnd In4 In3 In2 In1 L6506 Pwr En Sync Osc R/C U5 Vcc 12 13 14 15 16 17 18 19 20 OFFB OFFA Vsen1 Out4 Out3 Out2 Out1 Vsen2 Ref1 Ref2 SENSE1 PHASE4 PHASE3 PHASE2 PHASE1 SENSE2 2 3 PHASE3 3 % 1/4W 33K R29 C17 0.22uF 2 2 U8A 10K R30 1 20K 5K % 1/4W R24 R23 P5V 68 nF C14 2 3 PHASE2 GND 2 1 P5V 3 1 ENB VOUT R27 R28 1 5K % 1/4W R26 20K R25 1 P5V 20K 68 nF C15 20K 1 /4 W 1/4 W IN2 VIN 2 IN3 ENA 1 1 % IN4 IN1 + 78L05 P5V % PHASE1 100uF C16 U6 P15V 2 2 VREFA VREFB Figure 1c. Schematic diagram, page 3 1 1 2 2 2 1 4/7 www.st.com The L6506 regulates the motor current by comparing the voltage across sense resistors R10 and R18 to the voltage references. When the voltage across the sense resistor exceeds the reference voltage, the L6506 turns off the output and allows the current to recirculate until the oscillator turns the bridge back on. The value of the sense resistor and the reference voltage set the peak motor current according to the equation: Ipeak = VREF / Rsense For a typical application, the value of Rsense is chosen so that the voltage across the sense resistor at maximum motor current is between 0.5 and 0.75 V. Inputs IN1- IN4 control the phases of the bridge. If an input is high, the high side transistor of the corresponding half bridge will be turned on. If the input is low, the low side transistor of the corresponding half bridge will be turned on. Since the L6384 uses a bootstrap diode to power the high side gate driver, operation at 100% duty cycle on the high side is not possible. However, the L6506 ANDs the PWM signal to control the current with the logic input so that, as long as current is being regulated, the high side is switched at the chopping frequency and the bootstrap is always refreshed. ENA and ENB are the enable for the bridges. When ENA or ENB is low, all four transistors of the corresponding bridge are turned off. Jumper WJ1 is used to select fast or slow decay mode. Connector J2 is compatible with the PractiSPIN evaluation system. The board may be controlled from the PractiSPIN interface by selecting the L6207 in the device list. Variations The L6384E was selected for its logic compatibility with the L6506 and that it included dead time control. Other gate drivers that may be used are the L6390, L6391, L6392 and L6393 that are also logic compatible with the L6506. Support material Documentation Datasheet L6506, Current Controller For Stepping Motors Datasheet L6384E, High-voltage half bridge driver April 2012 DN0006 Rev 1 5/7 www.st.com Appendix A, Bill of Materials Comment Description Designator 0.22uF capacitor 1206 C1, C2, C3, C4, C5, C6, C7, C8, C17 1.0Uf capacitor 1206 C9, C10, C11, C12 680uF capacitor 1206 C13 68 nF C14, C15 100uF 100uF, 200V, Electrolytic C16 2.2 nF C19 1N4148WS D1, D2, D3, D4, D5, D6, D7, D8, D9, D10 34 pin flat ribbon connector J2 connector, Phoenix, 2 pos P1, P2, P3 connector, Phoenix, 2 pos P4 STP80NF10 MOSFET 60V TO220 Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8 200 capacitor 1206 R1, R2, R3, R4, R5, R6, R7, R8, R9, R12, R14, R17 0.1, 5W capacitor 1206 R10, R18 10K capacitor 1206 R11, R13, R15, R16 22 capacitor 1206 R19, R20, R21, R22 5K trimmer pot R23, R28 20K R24, R25, R26, R27 33K R29 10K R30, R32 4.7k R31, R33 2.2K resistor1206 R34, R35 L6384E Gate Driver U1, U2, U3, U4 L6506 Current Regulator U5 L78L05 5V regulator U6 74HC32 2 input OR gate U8 74HC08 2 input NAND gate U9 Jumper WJ1 Revision history Date 15-Apr-2012 April 2012 Version 1 Changes Initial release DN0006 Rev 1 6/7 www.st.com Please Read Carefully Information in this document is provided solely in connection with ST products. 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