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DRV8412: FAULT pin does not activate during over current condition

Alec Montandon
Prodigy 10 points
Part Number: DRV8412

A bit of Description:

I have a motor driver set up in Parallel full bridge configuration by setting M2 high, whist M1 and M3 are low.

Using a OC_ADJ pin of 150 Ohms.

This is all set up on the DRV8412DDWEVM Evaluation board.

The Top view of the board.

Power Rail set up

Power connections

Output Read(no CBC) 

Yellow: input PWM

Blue: output voltage

Green: output current

PWM output set up along with Signal readout.

The problem:

CBC current limiting should come into effect at 3.8 A, which it does, however the FAULT pin won't activate, I know the FAULT pin works as it functions for under voltage faults.

Output Read (with CBC)

Has anyone else had this issue? Or does anyone else have any idea why it might not work?

  • 0
    TI__Expert 4955 points

    Hello Alec, 

    I am happy to help out today. In parallel full bridge mode the device does not operate in latching mode, but rather in cycle by cycle (CBC) current regulation. Meaning that the current will shut down until the next cycle is triggered and nFault will not trigger low.

    nFault should only trigger once an OC latching shutdown happens meaning it can't happen in CBC regulation instead the device simply restarts once the next signal cycle arrives. 

    Section 7.4 of the datasheet shows how the device should operate under CBC current regulation. 

    Please let me know if you have any other questions or if I can assist you with anything else.


    Best,

    Pedro Arango Ramirez