• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 30 subscribers
  • Views 1099 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8701: The driver breakoff 24V 10A

Ger
Prodigy 40 points

Part Number: DRV8701
Other Parts Discussed in Thread: CSD19532Q5B

Hello TI Team!
We are using the DRV8701 to evaluate the possibility of drive two type of motor with the same design:
- 12V 20A max DC motor
- 24V 80A or 92A max DC motor
For this purpos, a simple electronic board was designed to test the motors.
We wanted to use the DRV8701P but I can't find it an we have used the DRV8701E with 4mOhm 100V CSD19532Q5B MOSFET .


- We tested the first motor (12V 20A) without problems. Increasing the mechanical load up to 30A. It runned fine.
- Then we tested the second motor (24V) but without mechanical load (about 10A). In a few short moviments (4-5 moviments of about 3 seconds). The driver doesn't run. The components are cold, no leds light and no smoke or fire (nothing). Only the drive is seems off. I tested the sleep pin and there is 3,3V but on DVDD and AVDD there are 0V. VM is OK... 24V.. the driver has broken. I don't understand, I was hoping that the MOSFETs could be broken by lager currents, but not the driver...
¿what could have damaged the DRV8701?
Thanks

  • 0
    TI__Guru 55765 points

    Hello,

    Likely an over-voltage happened to the driver and this caused a failure.  Please see this blog below:

    This is very common and we see it all the time.  

    https://e2e.ti.com/blogs_/b/industrial_strength/posts/art-of-stopping-the-motor-vm-pumping

    Regards,

    Ryan

  • 0 in reply to Ryan Kehr
    Prodigy 40 points

    Hello Ryan,
    Thank you for the quick reply.
    I had already seen this link. This is probably the problem, but we use this motors a lot of years ago, always with a electronic telecontrol and the same battery. we used the power control with a electromecanic inversor relé (big) istead of a H bridge . This is their schemme:

    there is hundreds intalations with this aplication driving 40-50A and never we have had problems with the DC/DC of the telecontrol electronic. We used the LT8640-1DC/DC (42V max) and TPS5430D (36V max). I thought, if they haven't breaked with electromecanic control, the BEMF is alway less that 36-40V... (too brak the motor)
    Does it makes sense that with mosfet, the BEMF are a lot of bigger that as electromecanic relee? (only with 10A it break...)
    Can have have another reason?

    To solved the problem, it occurs to me:


    1) suply the DRV8701 VM whit a resistor + 24V zener. Then I protect the DRV8701 of BEMF but other device supply of the same battery should resist the BEMF. Is it true? anything else to keep in mind?


    2) using coast to braked the motor with the DRV8701(all bridge Hi-Z) instead of slow decay. But the protection diodes of the mosfet will drive the BEMF current and they will break... right? so is it better decreasing input PWM duty directly to 0% and pray to the Mosfet hold up?

    I find it very difficult to get the goal with 60, 80 or 90A...
    any other advice or idea?
    I want to measure the real BEMF but first I need to protect the DRV8701 (I only have one...) What do you recommend me?
    Thank you very much!

  • +1 in reply to Ger
    TI__Guru 55765 points

    Hello,

    1)  This could be one method and also increasing bulk capacitance to absorb the current flowing thru FET body diodes.  

    2)  I would recommend slow decay to brake the motor or decreasing PWM duty cycle slowly.  Both are mentioned in the app note I linked.

    "Decelerating slower is the most straight forward way to reduce the reverse current. If we control the input PWM duty from 100% to 30% immediately, there is big VM pumping. But if we control the PWM duty from 100% to 30% gradually within 5 or 10 seconds, the peak pumping voltage is much lower.

    An interesting fact is that if we decelerate by decreasing input PWM duty directly to 0% at slow decay mode, then there will be no pumping at all. But, the H bridges should be able to handle the huge current caused by BEMF."

    Regards,

    Ryan

  • 0 in reply to Ryan Kehr
    Prodigy 40 points

    Ok Ryan,

    I will try to test with severals bulk capacitors and I will protect the DRV8701 with TVS diode. 

    Thank you very much!