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Zener diode selection in unipolar stepper motor(DRV8803)

Mohan Srinivasan
Prodigy 30 points
Other Parts Discussed in Thread: DRV8803

Hi All,

I just need to know how to select the zener diode (connection btwn VM and VCLAMP) in DRV8803 stepper motor driver design,

How much zener power dissipation rating need to select and how much zener voltage ? Do we have any formula to arrive this value ?

My design, motor voltage is 26V and motor current is 1.5A.. 

  • 0
    TI__Guru** 114905 points
    Hi Mohan,

    The selection of the optional zener voltage is based on the motor performance, the system voltage and the absolute maximum voltage of the DRV8803 .

    The power is based on the max voltage across the zener times the current. Please note the current could be up to 3A in your example if two outputs are disabled simultaneously.
  • 0 in reply to Rick Duncan
    Prodigy 30 points

    Hi Rick Duncan,

    Thanks for your reply..

    I captured the unipolar stepper motor (1-2 phase excitation) one pair of winding current and clock in one of the existing design and I am not understanding why the winding current toggle btw 0A to 2A between the clock pulse. Is there anything wrong or this is the expected waveform.

    Also pls explain how the negative current flowing in other winding (which path), whether the mosfet body diode conduct in reverse direction and following to other winding during kick back ?

    As per my understanding the current should be constant with ripples between the clock pulse.

    Ch1 - A winding current

    Ch2 - ~A winding current

    Ch3- Clock to motor driver