DRV8350: Short Circuit

Brian Wang0928

Genius 14090 points

Part Number: DRV8350

Customer made a short circuit between phase U and phase W by a short wire cable to make over current event.

Device:DRV8350HRTVR (HW version)

Detection Threshold is set as 0.7V by 75KOhm.

here are some questions.

- When nFAULT pin is pulled low after short-circuit event, why the PWM signal is pulled low immediately, but after 15uS, the PWM is active high, and then always low. Why?

- What is the response time to turn off the PWM signal, when nFAULT is pulled low? is it specified in d/s?

- When over current is detected by the each SHx pin, all PWM will be shunt down? Or only one phase will be shutdown with related SHx that is triggered?

over 2 years ago

0 Akshay Rajeev Menon over 2 years ago

TI__Mastermind 23556 points

Hey Brian,

Thank you for your question.

I will aim to provide feedback before the end of the week.

Best,
Akshay

+1 Akshay Rajeev Menon over 2 years ago in reply to Akshay Rajeev Menon

TI__Mastermind 23556 points

Hey Brian,

From the waveform it seems like VGS goes high as the nFault is being cleared which makes sense.

Also can you please provide waveform of VM, INx signal controlling the gate shown in your waveform, nfault and VGS while performing this test? I want to check if supply voltage is dipping.

Best,

Akshay

0 Brian Wang0928 over 2 years ago in reply to Akshay Rajeev Menon

TI__Genius 14090 points

Hello Akshay,

One more question, customer is more interested in that when one of UV, VW or WU phase is shorted, what is the architecture inside to protect against SC event?

Regards

Brian

+1 Akshay Rajeev Menon over 2 years ago in reply to Brian Wang0928

TI__Mastermind 23556 points

Hey Brian,

When you have a direct phase to phase short the most likely fault to trip is the VDS fault, as you have a large voltage being dropped across the MOSFET. You can find this out by checking the MOSFET RDS on and the VDS trip level to see at what current he VDS trips.

If this short draws excess current from your power supply then you can have a supply under voltage which can in turn cause gate voltage to drip and cause a VGS under voltage as well.

Hope this offers some clarification.

Best,
Akshay

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DRV8350: Short Circuit