DRV8305: DRV83053 fails quite often

Expert 2820 points

Replies: 15

Views: 381

Part Number: DRV8305

Hi,

Have been using the DRV83053 for a while; I've had successes with it, failures too. The board what I am using is my own, but is very similar to the BOOSTXL-DRV8305.

I've posted a picture of the board in this thread.

I am attaching the schematic here:

Previously, it was not quite evident what caused the failures, but recently I've been able to identify a bit more as to what's probably happening. Maybe the issue could be sorted out with some help and hence the post.

After fixing the issue as in my previous post. outlined here:

the board has been functioning and has been running quite well, even with motor being braked physically. It looked quite pretty.

Some days back

DRV8305 latest failure situation - Situation log
---------------------------------------
* Motor got stuck due to a mechanical fault, while running.

* SMPS tripped and shut down likely due to OCP

* Smell of cashews being roasted.

* Switched off Power

* Switched ON after a few minutes, SMPS powered ON. Motor does not run.

* No 3.3V LDO output on the DRV8305 - have a Green LED with 330 ohms connected to the LDO output. Likely draws about 10mA. The LED is not lit.


* Checking and looking deeper,
 - no visible burns/cracks:
 - Initial checks showed L1 (a 0.47Ohms resistor is connected in that position) went open

 - Looking deeper, C21, C22 (47nF) capacitors are shorted internally

 - Looking further, R5 100ohms resistor is open

 - C4 appears to be shorted internally.

 - MOSFET's appear okay, checking with a meter.

* Removed C21, C22 (47nF) capacitors
 - C21 is really shorted internally

 - C22 appears okay, checked with a LCR meter, shows 47nF

 - Checking impedance between DRV8305 Pins 43 & 42, it appears they are shorted internally.

 - Checking impedance between DRV8305 Pins 39 & 40, it appears they are shorted internally.

 - Removed C4 (2.2uF) capacitor, it appears okay, LCR meter shows 2.2uF

 - Checking impedance between DRV8305 Pins 38 & 41, it appears they are shorted internally.


So, it appears that the DRV8305 is dead too, without diving any further deep.

What could cause the charge pump capacitors to fail thus. This has been the standard way the failures has been happening each and every time. Once the bootstrap capacitor fails, likely the DRV8305 also fails. Thus the resistor too. This one problem is holding me back from proceeding on this project, for a while. Sigh!

I wonder what could be causing this issue ? Anything that could be changed in the design to avoid this issue over and over again ? (I have tried looking into each and everything that I could read about it, but cant seem to find what I am missing)

HELP! HELP! Can someone please help ?

Thanks,

Manu

15 Replies

  • In reply to Manu Abraham:

    Hi Manu,

    (8/7/19_4) The purpose of this schottky is  to take advantage of its low Qrr and reverse recovery time. This will help reduce the negative spikes. A TVS is better suited as a clamp.

    5A rating would be fine

    (8/7/19_6) I need a little clarification here. When you are running without a "nose plier" event and you progressively increase the load , does the DRV8305 get hot or is it only when you try to mess with it ?

    (8/10/19_7) I don't think a VDD to GND diode would help

    Yes, 15V/ 500mW is sufficient for the gate protection zener.

    Regards

    Anuj  

  • In reply to Anuj Narain:

    Hi Anuj.

    (8/7/19_6) The DRV8305 & the FET's were previously "getting hotter as the motor was revved up". It got "even more hot when I tried to mess with the spindle" with the braking test. I thought the FET's and the DRV8305 might blow up, being that hot. But it didn't.

    Attaching the waveform (across the motor U,V, W one phase) with the negative spikes, this waveform is with the capacitors on the board. (during Normal run. You can notice that there is noise in the form of ringing, as well as a negative undershoot)

    After the previous mail, I removed all the 6 100n capacitors from motor U, V, W to VDD and GND

    I did not have the Schottky diodes at hand and hence yet to order the same. It would take a few days for delivery. I have a few B140's with me.

    Was a bit impatient to try the B140 for the same use, from motor U, V, W to GND.

    Tried that, the results are:

     - The MOSFET's do not heat that that much, they become warm now.

    - The DRV8305 does not heat up, it is warm now, but it is with that huge heatsink (I wonder, whether the DRV8305 was really intended with a large heatsink. The 3 ounce copper PCB with thermal vias- via stitching does a good job, in other previous use cases.)

    - Retried the "hard brake" test. The SMPS does OCP shutdown. Power OFF & ON, the cycle was repeated a few times. Things do look okay. The DRV8305 is warm. MOSFET's slightly warm. Things look under control.

    (Haven't yet tried the Zener at the MOSFET gate yet. Do you still want me to try it ? Haven't got the Zeners at hand, yet)

    Attaching the waveforms across the motor U, V, W.

    The negative undershoots and the ringing seems to have reduced with the introduction of the Schottky diodes. Heat dissipation in all components seems to have drastically reduced. It looks god, I must say. The fix looks good. Schottky on U, V, W. Diode in series with VDRAIN resistor, Diode instead of the Inductor.

    What do you think about a small output L-C filter at the FET outputs (ahead of the newly fixed Schottky) ?

    Thanks,

    Manu

  • In reply to Manu Abraham:

    Hi Manu,

    (8/7/19_6) Yes, 5A Shottky is OK for Phase-GND

    VDD to GND will not help

    For the VGS protection, yes this will only handle peak currents so 15V/500mW is perfect

     

  • In reply to Anuj Narain:

    Hi Manu, 

    I wanted to check in on how your testing is coming along ? 

    Regards

    Anuj 

  • In reply to Anuj Narain:

    Hi Anuj,

    Got the components only today. It looks great as of now. DRV8305 seems quite okay. No issues it appears to be. Will fiddle with it over the week and see how it goes.

    Will update this thread in a few days time.

    Thanks a lot. Much appreciated.

    Best Regards,

    Manu