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DRV8848: Question for DRV8848 Output Voltage Spike

Part Number: DRV8848

Hi Team,

Our customer is using DRV8848 in their system to drive two DC motors, during the direction change, we will see some voltage spike on the rising and falling edge on the output pins as below. Our question is as our understanding, there should be internal MOSFET body diode to clamp these spikes, why we still see the spike which can go up to ~15V with VM=12V? Is there any risk for these spikes on the output pins?


  • Hi Jacky,

    The function of the internal FET body diodes is to carry the current for brief moments when switching the FETs to prevent the high side and low side FETs of the same half bridge from conducting at the same time. These spikes can occur if there is significant trace inductance on the PCB which can create LC oscillations with the FET capacitance. These voltage spikes can potentially create large current spikes at the output that can damage the device and other components on the board. Another potential risk of having high voltage spikes is higher EMI noise.

    To protect against these spikes, you can place RC snubbers across the FETs to damped the oscillation spikes. You can also place varistors across the outputs to limit the spikes. 

  • Hi Pablo,

    Thanks for the feedback. But we do try below methods to clamp these spikes on the output pin, and no obvious improvements:

    1. By adding clamping diodes on output pins, no improvements, still can see high voltage spikes during motor reversing.

    2. By adding R-C snubbers on output pins, no improvements, still can see high voltage spikes during motor reversing.

    3. By adding TVS diodes on output pins, no improvements, still can see high voltage spikes during motor reversing.

    So, can you help to share more experiences how do clamp these spikes on the motor output pins when suddenly change the motor direction? Thanks.

  • Hi Jacky,

    If the clamping methods are not working it could mean there might be issues with either the schematic or layout. if the layout is not optimized to reduce the oscillations, then no amount of suppression methods will help. If you are willing to share your design schematic and layout (at least the section with the motor driver and output stage), I can review it and see if there might be issues with your design causing these oscillations. you can send the documents via private message if you wish.

    I have a question in regards to your procedure for reversing the motor direction. Can you tell me the exact procedure you used to reverse the motor direction?