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DRV8876-Q1: Additional protection for DC motor drive

Jishnu K.
Prodigy 30 points
Part Number: DRV8876-Q1
Other Parts Discussed in Thread: DRV8876

Tool/software:

Hello Team,

I'm designing a motor drive for DC motor of power rating 12W and the input is a 12V system. I considered DRV8876 as the driver IC and it I'm following the reference given in the datasheet. Apart from the inbuild protection technique, I would like to introduce some protection technics in the load side (using some capacitor, diode). Unfortunately, my driver circuit will be away from the motor  and the connection is established using long wire. Is there any recommended technic for the load protection? Since the due to the long wire (1m), there will be some effects due the wire transient.

Thank you.

Regards,

Jishnu

  • 0
    TI__Mastermind 44995 points

    Hi Jishnu,

    Thanks for posting in this forum.

    Jishnu K. said:
    I would like to introduce some protection technics in the load side (using some capacitor, diode). Unfortunately, my driver circuit will be away from the motor  and the connection is established using long wire. Is there any recommended technic for the load protection? Since the due to the long wire (1m), there will be some effects due the wire transient.

    This is a valid concern. Such long wires have parasitic inductance that may affect the behavior at OUT1 and OUT2. You may TVS diodes rated slightly higher than the VM supply voltage, as shown below to protect from voltage spikes. Optionally, you may also add four external Schottky diodes, one each in parallel with the body diode of each FET in the H-Bridge. Usually a capacitor right on the motor itself will help mitigate EMI due to brushes commutation spikes as well as two capacitors near the motor connection point on the PCB. The TVS also would be closer to the motor connection point on the PCB. In some cases the capacitors alone may be enough to mitigate the spikes. 

    Regards, Murugavel 

  • 0 in reply to Murugavel4637
    Prodigy 30 points

    Hello Murugavel,

    Thank you for the reply.

    I found this answer very helpful. I would like to know bit more about the schottkey network. If it possible please share any documents related with sizing of Schottky network. I appreciate any kind of response.

    Regards,

    Jishnu K

  • +1 in reply to Jishnu K.
    TI__Mastermind 44995 points

    Hi Jishnu,

    Glad my previous answer was helpful. Please mark this thread as RESOLVED. 

    Jishnu K. said:
    I would like to know bit more about the schottkey network. If it possible please share any documents related with sizing of Schottky network.

    This is not a special Schottky network. Each Schottky diode should be connected in parallel to the MOSFET body diodes - see below block diagram showing the four body diodes. Regarding the sizing, they must be rated for the device absolute maximum VM voltage 40 V and must be able to support the peak load currents, for example a BDC motor startup inrush current as a general guideline. Thank you. 

    Regards, Murugavel 

  • 0 in reply to Murugavel4637
    Prodigy 30 points

    Hello Murugavel,

    Thank you for the explanation. I really appreciate your help and your answer was something I was exactly looking.

    Thank You.

    Regards,

    Jishnu K

  • +1 in reply to Jishnu K.
    TI__Mastermind 44995 points

    Hi Jishnu,

    That is good to know. Thank you! 

    Regards, Murugavel