DRV8844: VM pin burned issue

Cherry Zhou

Part Number: DRV8844

Hi Team,

The customer is using the DRV8844 to drive a DC motor, the IC body is damaged when the motor is running properly. Based on the pictures below, pins 4, 5, 10 and 11 are broken which is VM and OUT. The VM is connected to a 24V supply. Is this issue due to:

1. Transient Overcurrent (such as shorted internal to brushed motor)

2. VM overvoltage damage (such as power supply misconnected above 24V)

Could you help check this case? Thanks.

Best Regards,

Cherry

over 1 year ago

0 Keerthivasan Kumanan over 1 year ago

TI__Mastermind 18425 points

Hi Cherry,

Does the motor spin for a while and then the IC burns out or is it instantaneous. Are you doing anything with the INx signals before burnout? Have you gotten any scope captures. If not I reccomend capturing VM and. Does nFAULT ever go off and can you figure out if it is OCP. Here is a good resource on VM pumping:The art of stopping a motor – VM pumping - Industrial - Technical articles - TI E2E support forums. Can you tell me more about the conditions that led up to the damaged IC (signals they provided/ changed)?

Best,

Keerthi

0 Cherry Zhou over 1 year ago in reply to Keerthivasan Kumanan

TI__Mastermind 22235 points

Hi Keerthi,

Thank you for the support.

Keerthivasan Kumanan said:
Does the motor spin for a while and then the IC burns out or is it instantaneous.

The IC burns out after the motor has spin for a while.

Keerthivasan Kumanan said:
Are you doing anything with the INx signals before burnout?

It has been reversed before burnout.

Keerthivasan Kumanan said:
I reccomend capturing VM and

VM is supplied from a power pod and is stable at 24Vdc.

Keerthivasan Kumanan said:
Does nFAULT ever go off

Goes off until it has burneout, so the protection is normal.

Keerthivasan Kumanan said:
can you figure out if it is OCP.

The supply voltage is 24V, are you referring to that according to the figures above, is the IC damaged possibly due to OCP?

Thanks and regards,

Cherry

0 Keerthivasan Kumanan over 1 year ago in reply to Cherry Zhou

TI__Mastermind 18425 points

Hi Cherry,

How fast are they switching directions. What kind of decay mode do they use in between changing directions. Can you send me a schematic? Do they have an EVM, and can they try the same thing on the EVM?

Best,

Keerthi

0 Prajwal Nataraj over 1 year ago

Prodigy 30 points

Hi Keerthi and Cherry,

I too am facing the same issue where the VM pin was burnt, from that moment I am using a power supply with current limit to check the working.
So, now the pins are not burnt due to the current limit but the IC does get damaged.
In our case too, it happens during direction change. Its in slow decay mode.
It happened when the direction switch time was set to 50ms.

Regards,
Prajwal

0 Keerthivasan Kumanan over 1 year ago in reply to Prajwal Nataraj

TI__Mastermind 18425 points

Hello Prajwal,

Are you using our EVM. Do you have scope captures as well as. If not, can you try on our EVM or send a schematic. I will look into this and give an update by next week.

Best,

Keerthi

0 Jacob Thompson over 1 year ago in reply to Keerthivasan Kumanan

TI__Mastermind 23421 points

Hey Cherry,

This definitely looks like an overvoltage event. In this case, likely due to the rapid motor reversal from your comment "It has been reversed before burnout."

Please read The art of stopping a motor – VM pumping. When the motor direction was changed, this caused a rapid rise in the VM voltage beyond the maximum voltage the device could handle.

To avoid this situation, you should PWM the input signals to ramp down the speed of the motor in a controlled manner and then accelerate/ramp-up the PWM to start the motor again.

You can also see Part 2: How to estimate motor regeneration and VM pumping.

Prajwal correct, the built-in protections of this device do not include overvoltage protection unfortunately.

Best,

Jacob

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DRV8844: VM pin burned issue