When using DRV8307 , what do you recommend to prevent it from damaging when driving high current load ?

Michael, it would be helpful to know how the DRV8307 is failing.  For example, does it develop a low-resistance path from VM to GND?  Do VINT and VREG no longer measure 1.8V and 5V?  Or what else is the behavior?

Also, if you haven't already, you can confirm that it really is the DRV8307 that's failing by re-soldering a new IC and seeing if the board starts working.

If I had a guess a reason, it would be overvoltage.  When you drive more current, it is normal for voltage noise to also increase.  The SI9979 has absolute max ratings that are about 10V higher than the DRV8307.  Now one note here is that the DRV8307 has a stated absolute max VM of 35V, but we are in the process of updating the documentation to 42V.

Can you measure VM to see what voltage it's reaching?  Wilson wrote 2 app notes on VM pumping that you might find helpful: this and this.  Also, make sure you have adequate bulk capacitance.

Best regards,
RE

Thanks for your reply. The failure is that VM is shorted to the GND, and the chip got hot when running it again.

I assume you've verified that the short goes away when you desolder the DRV8307 from the PCB?

So in addition to increasing bulk capacitance, other things that can help your situation are:
-When turning off the motor, use coast instead of brake.
-Add a TVS diode to your board with an appropriate power rating.
-If your FETs are turning on too fast and causing noise, slow down the turn-on time by adding series resistors with the gate drivers.

Best regards
RE

Hi RE,

How to use coast on DRV8307 ?

I will increase VM cap to 470uF to try.

I have TVS already, it is 33V type. I may change to 27V.

If I use a separate +24V regulator for VM, will it be helpful to isolate VM from main motor power supply ?

Thanks,

Michael 

Have you confirmed the DRV8307 is developing the short, and not some other board component like your TVS?

Bringing ENABLEn high and leaving BRAKE low makes the motor coast.

The DRV8307 measures the VDS across the external FETs for fault protection, so it's not recommending to use separate supplies.

Best regards,
RE

Yes, the DRV8307 was developing high current on VM and got hot. I replaced it, the board works again with light load.
Here are some more questions:
1. When stopping the motor, the software pulls ENABLEn high first and then apply BRAKE High to brake. The question is how long has to be there between the 2 operations.
2. According to the datasheet, the recommendation for over 350W motor drive, the VM bulk cap may reach 2200uF or higher. Is it necessary to be that big size?
3. Does TI have any high power application notes with DRV8307 ?

1. Ok, so braking is currently being used. That might be what's causing an elevated voltage. To answer your question, there's no requirement to separate the time between changing ENABLEn and BRAKE. For systems that want brake behavior instead of coast, I even recommend tying these inputs together.

2. The amount of bulk cap needed is a tricky question, and system-dependent. If you're able to easily reproduce the problem, you could try adding excessive capacitance and seeing if the problem goes away. Then reduce it until it shows up. Better yet is if you can scope the voltage noise that we suspect, since that's easier to work with than checking when units go bad.

3. No, sorry, we don't.

Best regards,
RE

Hi RE,
Just thinking out of the box, beside VM, there are 3 other pins directly connected to the high power side, U,V, W, is it possible that any high voltage on those pins causing the ship damage ?

I will keep you post and share the data once I get this work reliably.

Thanks,
Michael

If the DRV8307 outputs don't develop shorts on damaged devices, and it's just VM to ground, then I don't suspect the output side is a problem.

Best regards,
RE