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DRV8302: DRV 8302 destroyed

Thilo Binder
Prodigy 170 points
Part Number: DRV8302

Hello,

I’m still struggling with my DRV8302 design. My old DRV 8302 Design finally worked very fine, but to prevent high inrush current i switched on power by adding a 100R series resistor before switching on completely.

In my new design i separated the final stage voltage and the DRV 8302 voltage. The operating voltages comes from the same power supply but the final stage voltage is switched on later by a soft start circuit. When i now connect the DRV 8302 operating voltage directly to a Battery or Power supply , the DRV8302 gets destroyed immediately .I tried this on different PCBs. This happens with 48V an even 36V battery voltage. When i first connect the PCB to a power supply and switch on the power supply (may start softly) everything is fine. Any ideas? Do i have to add a protection device? Or ist the separation between the power stage and the DRV8302 voltage a problem? The explosion or smoking spots are always near pins 53/54 or pin29.

 

Regards

Thilo

 d

  • 0 in reply to Thilo Binder
    TI__Guru 65250 points

    Thilo,

    It sounds like you are applying power to the Bridge before the DRV, correct?

    Have you checked the SL, SH, GL, and GH nodes with a scope after you turn on the bridge power but before you turn on the DRV?

    Have you tried powering the DRV first before the bridge?

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Prodigy 170 points

    Hello Adam,

    No, vice versa. First i power up DRV 8302. Ahter the 12V power supply of the DRV 8302 works, the Final stage is powered up softly.But in most case the DRV 8302 is destroyed in the first miliseconds before something further could happen.

    Regards

    Thilo 

  • 0 in reply to Thilo Binder
    TI__Guru 65250 points

    Thilo,

    Could you post a higher resolution schematic please? I cannot read the component values.

    Regards,

    -Adam

  • 0 in reply to Thilo Binder
    TI__Guru 65250 points

    Thilo,

    Can you show us a scope image of the PVDD1 and PVDD2 power up sequence? I want to see the timing of those signals.

    Also is it possible to use separate supplies to power PVDD1 and then PVDD2 with current limiting to a very low value? After these supplies are up 

    I would remove Q7 and Q8 for debug purposes as I am not certain if they are causing an issue here.

    Your DVDD and AVDD capacitance is also much bigger than recommended, I'm not sure if this is causing a current in-rush issue. Can you replace the AVDD and DVDD capacitance with 1uF total?

    Please also remove one of the two GVDD caps to bring the capacitance to 2.2uF total.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Prodigy 170 points

    Hello Adam,

    In the meantime i have found the following solution: Because i can not accept high currents (sparks) while connecting the system to he battery i added a softstart resistor (4,7Ohm) between Battery and PVDD. Also i charge the final stage capacitors by a 47 Ohm resistor. After the final stage capacitors are (almost ) charged i switch on a relay which bridges both  resistors. Now everything seems to work properly and savely . If there were further issues i will consider your suggested solutions. I hope i must not annoy again :)  Thanks for your response.

    Regards

    Thilo