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Original question:

DRV8870: The VM power pin is burned out

DRV8870: VM pin burn out problem

Darren Wen
Prodigy 270 points
Part Number: DRV8870
Other Parts Discussed in Thread: DRV8231A, DRV8231

Hi team, 

There is a DRV8870 failure case need your comments. Customer find that there are two pcs DRV8870 broken down, and both are VM pin burned out. 

Customer application: the VM voltage no higher than 17V, and the current not higher than 1.2A, both are far away the threshold and many buffer.  

1. Could you help to provide your comments for the root cause of this case?

2. We find there is a similar case VM broken case in e2e forums, the link is https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1214985/drv8870-the-vm-power-pin-is-burned-out?tisearch=e2e-sitesearch&keymatch=DRV8870# . Do you think it is a comment problem in application? 

3. Please help to provide comments about how to avoid this type failures? 

Thank you.

 

  • 0
    TI__Mastermind 22240 points

    Hey Darren,

    Can you also provide me your PCB layout used on this board to review? 

    What is the value of the bulk capacitance used in this system? 

    What is the value of your sense resistor? I think I only have small partial schematic from email, wondering what else might be affecting the VCC_SYS voltage.  

    And what does the DRV8231A on your schematic mean? 

    Thanks

  • 0 in reply to Jacob Thompson
    TI__Mastermind 22240 points

    Design information
    SCH as below, the OCP design as 2.1A, and the load is brush motor, the resistor of motor is about 8ohms, and the rated voltage is 14.4V

    For software design, they measure the current and the protection threshold is 1A, if continuous 5 time exceed 1A, then shut down the motor driver.  

    1. the bulk cap is 47uF, and the sense resistor is 0.02ohms. And Vsys design not higher than 17V, and test with different load also show the Vsys change not exceed Vsys±0.6V
    2. DRV8231 just for compatible design, and the device use in the board and mass product are all DRV8870

     

     

  • 0 in reply to Jacob Thompson
    TI__Mastermind 22240 points

    Hey Darren,

    One issue with the layout is the GND connection on the device.  It looks like it drops down to another layer through 3 vias and then connects to GND through a 0Ω resistor.  We recommend instead connecting it to the top side of the PowerPad.  

    Beyond that, system-level ESD (electrostatic discharge) can also cause this type of damage.  Have you tested for that?  See Design considerations for system-level ESD circuit protection

    Regards,

    Jacob

  • 0 in reply to Jacob Thompson
    TI__Intellectual 1380 points

    Thanks for your support! I have other two questions from customer side:

    1. As both of failure ICs have VM pin burnt out and short to GND, is it possible that the motor load is not matched? We recommend what is the suitable load range?
    2. Based on our past experience, is it more likely to be caused by customer design, or be individual failure?

  • 0 in reply to Amber Si
    TI__Mastermind 22240 points

    Hey Amber,

    Amber Si said:
    1. As both of failure ICs have VM pin burnt out and short to GND, is it possible that the motor load is not matched? We recommend what is the suitable load range?

    I don't think this is an issue with the load current - the DRV8870 can handle 3.6A, so your load of <=1.2A should be no problem for the thermal current. 

    Amber Si said:
    2. Based on our past experience, is it more likely to be caused by customer design, or be individual failure?

    It could be a lot of things, but typically not the DRV8870 device as the root cause.  This case is likely an individual failure but could be caused by an external factor that is not protected by customer design - such as an ESD event.  It could also be an overvoltage event from the load, a manufacturing defect in the board, or other environmental factor. 

    Regards,

    Jacob