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DRV8704: Under voltage (undershoot) on the switching node

Danny St-Martin
Prodigy 20 points
Part Number: DRV8704

Hi

I'm currently using an DRV8704 to drive a linear motor actuator, When I'm measuring MOT0A vs GND, I can see a negative voltage of -8.7V, it’s quick, around 10ns.

I’ve tried to remove it by adding 2 Schottky diode, one between MOT0A and Drain, the other one between MOT0B and Drain. The negative spike is still there.

The DRV8704 setting are:

                 CTRL- > DTIME = 880-ns dead time

                OFF -> PWMMODE = 1: PWM control mode

                DECAY -> DECMOD = 000: Force slow decay at all times

                DRIVE -> TDRIVEN = 11: 2.10 µs

                               TDRIVEP = 10: 1.05 µs

                               IDRIVEN = 10: 300-mA peak (sink)

                               IDRIVEP = 10: 150-mA peak (source)

 

When AIN1 = 0,  we are in cost mode

 

I was wondering if the negative voltage can be damaging the DRV8704?

 

In the datasheet its abs maximum is -0.6V, even in the curve from datasheet ’’ Figure 19. Current Regulation ’’  we can see a -4V.  

 

 

Regards

      

     

  • 0
    TI__Mastermind 37683 points

    Hello Danny,

    The spikes are very short (~10ns) so there is little risk of damage. However, it is always good practice to smooth out these spikes to prevent potential damage.

    This FAQ provides solutions for reducing voltage spikes. My main recommendation is to lower the IDRIVEN and IDRIVEP to slow down the output slew rate. This should lower the spikes. If it does not, let me know and we can try other solutions.

    Regards,

    Pablo Armet