DRV8844: nFault triggered when VM powering up

Hi Ryan,

But it is not acceptable in my customer's application. And as I mentioned, they noticed it depends on VM slew rate, and what they want to know is what slew rate will not trigger this weird fault and if this can be avoided by controlling the VM slew rate.

Thanks!

Jayden Li

Hi Ryan,

They need to know the specific data, like which slew rate, how much time will cause this unexpected issue? Thanks! 

Thanks!

Jayden Li

Jayden,

You said that the customer can't increase the slew rate, so why does in matter if they can't do anything about slew rate?

We need to find another way.  What is the length of the low pulse?  I can't tell from scope capture.  Do they monitor it with software?  

They can make a software change to filter it or it can be filtered in hardware with a capacitor.  

Regards,

Ryan

Hi Ryan,

I am trying to convince my customer if they can change the slew rate, but they need to know what slew rate is a guaranteed value for avoiding this nFault trigger. And then they can evaluate if they will control slew rate within this value.

Thanks!

Jayden Li

Jayden,

I am sorry, but I don't think there is a simple answer here.

Can you share the schematic?  Are LGND/GND connected together and to ground plane?  What is the state of nSLEEP and nRESET?  

Regards,

Ryan

Hi Ryan,

Due to the urgency, I reached you through WEBEX to close this asap. You can find my answer in WEBEX window.

Thanks!

Jayden Li

Jayden,

I will wait for your reply here as I requested.  I would like to see nSLEEP/nRESET on same scope capture.

Regards,

Ryan