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DRV8313: Overcurrent protection issue

Steffen Weiß
Prodigy 10 points
Part Number: DRV8313

Hello Team,

The overcurrent protection does not work for the case if the outputs OUT1 and OUT2 have a extern short-circuit.
(only an additional external measure resistor of 50mOhm is located between the both outputs).

Power supply: Vcc=48V, 5A limited, additional a capacity of 470 µF between Vcc and Ground on the DRV8313 test board.

1. Does the overcurrent protection not work if both outputs are short-circuited externally?

2. Is that possible that the FETs are demaged before the time "parameter overcurrent protection deglitch time" of 5µs is elapsed (and during this time the current is too high)?

The Fault pin is not checked and a sinussodial PWM is always on.

In that case the silicon is damaged on all four FETs on OUT1 and OUT2 (short-circuit).

See following circuit:

With best regards

Steffen

  • 0
    Genius 5040 points
    Steffen Weiß said:
    Power supply: Vcc=48V, 5A limited

    The chip internal current limit could be 3A, so it is not reliable to operate it at 5A. The spec say the internal current protection is 5A, but it could trip at 3A which is guaranteed. 

    Steffen Weiß said:
    2. Is that possible that the FETs are demaged before the time "parameter overcurrent protection deglitch time" of 5µs is elapsed (and during this time the current is too high)?

    Yes, I think so, as the short outputs caused a very high current through the FETs in a very short time before the 5us deglitch filter.

    Brian

  • 0
    TI__Mastermind 18916 points

    Hi Steffen, 

    Thanks for posting your question on e2e motor drivers forum - 

    I've assigned this thread to a team member and we'll aim to provide a response on timeline/answers by middle of next week 

    Best Regards, 
    Andrew 

  • 0 in reply to Andrew Liu
    TI__Genius 17416 points

    Hey Steffen,

     

    I would first reduce the current limit on your power supply to maybe 2A.

     

    If a shoot through condition occurs then the OCP should have shut down the H-bridge.

    Could you provide waveforms of the phase current and nfault to see if the overcurrent limit is being triggered? If the current is too high and a shoot-through occurred it is possible that the FET may have been damaged before the deglitch time.

     

    Best Regards,

    Akshay