DRV8412: Fault pin is not working

Javier Zamorano

Part Number: DRV8412

Hello,

During an initial test of getting the device to a fault state, I noticed that the outputs do shut off but the fault pin does not go low.

After looking into this with an oscilloscope I saw that during the time it goes on the fault line and AGND seem to increase by 1.6V!!!

Do you think I have a grounding issue? The mode pins also connect to AGND, so what behavior can happen if all mode pins go to 1.6V

I am using mode 1 and I have done this before with the DRV8412DDWEVM and the fault pin works there with the same test.

over 7 years ago

0 Rick Duncan over 7 years ago

TI__Guru** 114905 points

Hi Javier,

A grounding issue cannot be ruled out.

Mode 1 (CBC) will cause the outputs to disable until the next PWM cycle, but will not assert the nFAULT. Is this what you are observing?

Have you changed the value of the OC_ADJ resistor?

0 Javier Zamorano over 7 years ago in reply to Rick Duncan

Prodigy 30 points

What I am observing is seeing it try and turn on for a few milliseconds then shutting off.
When I used the dev board it did the same thing but actually changed the fault pin
We have not changed the OC_ADJ resistor.

0 Javier Zamorano over 7 years ago in reply to Javier Zamorano

Prodigy 30 points

Looks like changing the PWM cycle does make the fault pin work
In some cases I do have to run it at 100% PWM, so I am wondering if it is a good idea to start at CBC mode then switch to OC latching while it is turned on. Is it safe to change modes when the motor driver is operating?

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DRV8412: Fault pin is not working