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DRV8870 Motor current wave oscillation

masahiko shimizu
Guru 11235 points
Other Parts Discussed in Thread: DRV8870

Hi,

My cutomer is using DRV8870.
He has a issue which is motor current wave oscillation.

This issue occur only with capacitor at internal motor.
Capacitor is Electrolytic capacitor.

Please see the picture below.
Ch3 is OUT1 voltage and Ch1 is current output to motor.

And customer setting of current chopping is Rsence=0.1ohm and Vref=3.2V.

This issue occur at only using motor which has internal capacitor.
and This issue likely occur under High temperature
At using motor without internal capacitor, This issue does not occur.

I guess that the cause is inrush current by internal capacitor at FET turning on.
Is there solution for this issue?


Best regards,
Shimizu

  • 0
    TI__Guru** 114905 points
    Hi Shimizu-san,

    You are correct. The inrush current of the capacitor appears to be causing the device to enter current regulation.

    Is it possible to lower the internal capacitance of the motor?
    If not, adding a ferrite bead or inductor may help by reducing the inrush current.