DRV8718-Q1: offline diagnostics time

Wu JW

Part Number: DRV8718-Q1

Hi, Team,

My customer found the offline diagnostic time for the OLSC should be so long. Customer enable the OLSC by EN_OLSC, then setting the PD_SHx and PU_SHx in 10ms. They found the SHx pin should take >1 second to change to 1/2 VDD, which should be the right status for the DRV8718. And customer need to wait >1s to get the right diagnostic result.

Is it the normal working process for the DRV8718? Can we reduce the diagnostic time for DRV8718?

Following is the waveform, and the green one is the SHx's output.

over 2 years ago

0 Wang5577 over 2 years ago

TI__Guru 56650 points

Hello, WJ,

According to your test waveform, it is the normal. I don't find a way to reduce the DRV8718 offline diagnostic time.

Regards,

Wang Li

0 Wu JW over 2 years ago in reply to Wang5577

TI__Intellectual 2935 points

Do we have the more detail spec for the delay time? We can't find it in our datasheet. Is there any different for the time with different ICs?

0 Ryan Kehr over 2 years ago in reply to Wu JW

TI__Guru 54645 points

JW,

I am investigating this.

Regards,

Ryan

0 Ryan Kehr over 2 years ago in reply to Ryan Kehr

TI__Guru 54645 points

JW,

1) How is the load connected? Between two half-bridges?

2) Is the customer enabling PU and PD on the same half-bridge?

3) Procedure should be to enable PU on one 1/2 bridge and PD on the other 1/2 bridge (one on other side of load).

Regards,

Ryan

0 Wu JW over 2 years ago in reply to Ryan Kehr

TI__Intellectual 2935 points

1. The following picture demonstrate the connected load. Use DC motor to replace BDC.

2. For OLSC, enable PU and disable PD of one half bridge while enable PD and disable PU of another half bridge.

3. Yes , we enable PU for only one half bridge and enable PD for another half bridge like the figure above.

0 Ryan Kehr over 2 years ago in reply to Wu JW

TI__Guru 54645 points

JW,

It appears that everything was done correctly. Let me discuss internally.

Regards,

Ryan

0 Alpha Han over 2 years ago in reply to Ryan Kehr

TI__Expert 3750 points

Hi, Ryan:

Any update for the case?

Thanks

0 Wang5577 over 2 years ago in reply to Alpha Han

TI__Guru 56650 points

Alpha,

I saw system engineer recommendation: "do an experiment with only enabling the PD to see if that helps the discharge rate. Enable the PD first and leave it on for a period of time to discharge the SHx voltage (before enabling the PU)."

Regards,

Wang Li

0 Wang5577 over 2 years ago in reply to Wang5577

TI__Guru 56650 points

Alpha,

BTW, I didn't find anything wrong with your setting and sequence. Please let me know if the system engineer recommendation helps or not?

Regards,

Wang

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DRV8718-Q1: offline diagnostics time