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DRV8825 design

Radovan Petrovic
Prodigy 30 points
Other Parts Discussed in Thread: DRV8825

Dear,

I made design with DRV8825 IC, running it with motor Nanotec ST4118X0404, http://en.nanotec.com/steppermotor_st4118.html. I'm using Slow decay mode, 1/16 microstep mode, Rs is 1.3ohm, reference voltage is 0.95V, current is about 130mA. Everything works fine, but have question:

1) Are Mosfets diodes enough, or i need additional protecting diodes, because of Back EMF ?

2) I need it to run on 17 and 34 VDC supply voltage independently. Higher supply voltage makes more torque, and noise, and i can not lower current enough, to reduce it. Is it possible to reduce noise, to be similar on both voltages ?

3) Current is loosing adjustment given by formula below 0.9VDC reference voltage ?

Thank You, DRV8825 is good product.

  • 0
    TI__Expert 7455 points

    Hi Radovan,

    You do not need to add external diodes to operate the DRV8825. The internal body diodes will be enough to deal with current regulation during the asynchronous portion of the cycle.

    There are different mechanisms you can employ to decrease noise such as decreasing current, using mixed decay mode or increasing microstepping resolution. Each will pose its advantages and disadvantages, so to have the exact same noise level for both 17V and 34V will be tough. Some experimentation will be needed, but some compromise will be required as well.

    Current regulation has some limits. When decreasing the VREF voltage you cannot go to a current setting which requires a PWM duty cycle smaller than that imposed by the MIN TIME ON or TBLANK.

    Hope this info helps! Best regards,

    Jose Quinones