DRV8305-Q1: AVDD reads 0V

Bob,

Do you suspect the DRV got damaged? Have you tried another IC?

Regards,

-Adam

Hi Adam,

If AVDD is zero and the gate driver won't pass UVLO test at powerup but DVDD is 3.3V, VREF/VREG is as expected, etc, and I have no way to troubleshoot AVDD, then I suspect the DRV chip has been damaged. 

I noted that a low side transistor failed so I replaced that and the DRV IC, then added diodes in parallel with the low and high side transistor body diodes as well as a zener diode in parallel with the current sense resistor.

For what it's worth I am using CSD19536KCS, with PWM input (no higher than 20KHz) coming from a launchpad running the TI labs.

Best,

Bob

Bob,

Has this resolved the issue?

Regards,

-Adam

I suspect there are errors on the DRV8305-Q1 specification sheet published July 2019 and have made adjustments to my circuit board and am seeing considerably better results. There is an issue with latched faults now but at least the DRV IC appears to be recovering nicely.  I'll report more when I make further improvements.

Hi Adam. 

I'm working with Bob on this project with the DRV8305 chip and we are still getting failures. 

We have noticed that on the DRV8305 datasheet your schematics all show that SPx is tied to ground and SNx is tied to the high side of the sense resistor. In the layout recommendation you have this swapped, SPx is tied to the high side and SNx is tied to ground. We have also seen on a different TI design guideline to have SNx tied to ground and SPx tied to the high side of the sense resistor. Can you clarify which of these notations is correct (we've had many failures of the chip when designing based of of the schematic on the datasheet)? 

On 1 of our circuit boards we have shorted the sense resistor as seen in another forum post and the motor seems to be working without blowing the AVDD signal. We are also using a 3rd party micro-controller to interface with this board to run the motor. This can be a temporary solution but we need the current sensing capabilities of this chip.

On a second board (same design as first) we have swapped the SNx and SPx signals so SNx is now on ground and SPx is on the high side of the sense resistor. Attempting to run a motor with this is still damaging the DRV and we are getting an AVDD fault. With this board we are using the TI launchpad. One of the low side transistors is also reading a low resistance between the Drain and Source, there are fly-back diodes between the drain and the source of each transistor to protect the transistor from high induced voltage spikes, there are also zener diodes on the SPx pin to protect it against any voltages above 4.3V

Both of the boards have the fly-back diodes 

Any help on why this AVDD signal keeps going will be very helpful.

Thanks,

Kevin 

Kevin,

Did you resolve this issue?

Regards,

-Adam

Adam, 

No, we have still been unable to resolve the issue. Any insight on the issue that you or someone at TI can provide would be very beneficial, if you require more information as well please let us know. 

Thanks,

Kevin 

Kevin,

I saw in another post that this issue was resolved, is this the case? Some excess solder was found that may have contributed to the device damage.

Regards,

-Adam

Hi Adam, 

No the issue is still not resolved. That other post was from back in July, after that one had been marked as resolved and we still had the issue we had to open a new post, this one, to continue getting support for the issue. Though the excess solder could not have helped, it is not the underlying issue.

Thanks,

Kevin 

Kevin,

Bob mentioned getting better results and commenting again when his improvements were complete, did those changes get made or are they still pending?

Regards,

-Adam

Hi Bob,

I am closing this thread for now. If you have more questions can you please click "Ask A Related Question".

Regards,

Michael