DRV8353: Drv8353 fault pin drop to 1V when the en signal is enabled

sirius wang

Part Number: DRV8353

Tool/software:

Hello,everyone,

When tests the drv8353SR, we have two questions:

1.When disabled the PWM input , set the EN signal enabled,after 15us, The fault pin drops to 1V, ,through the spi read the fault code is 0X700， then enable the PWM input，it also work normally.

What causes the fault signal? Is the chip bug?

The waveform diagram is as follows（CH1-EN pin，CH3-fault pin）

2. When PWM is on at the rising edge, we find that the SOA/SOB/SOC signal drops to 0，We found that the SOA signal dropped before the Pwm was turned on，then we change the SPA/SNA resistance R172/R173 from10R to 0R，the SOA/SOB/SOC signal is OK，how this SPA/SNA resistance Impact SOA signals？

The waveform diagram is as follows（CH1-SOA pin，CH3-SHA pin）

1 month ago

0 Yara Al Shami 1 month ago

TI__Expert 7215 points

Hi Sirius,

Is this related to your other post?

https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1400656/drv8353-drv8353sr-pwm-fault

Regards,

Yara

0 sirius wang 1 month ago in reply to Yara Al Shami

Prodigy 20 points

yes,I didn't realize at first that I was Posting Chinese content on English forum? Then I reposted it in English

0 Yara Al Shami 1 month ago in reply to sirius wang

TI__Expert 7215 points

Okay sounds good, I will close the other thread and continue support here.

I found another E2E post that seems to have a similar problem: https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1039900/drv8353r-the-fault-pin-generates-a-negative-pulse-spike-when-the-drv8353-is-enabled

Let me know if this is any help

As for you register settings I don't think anything needs to be changed yet.

Regards,

Yara

0 sirius wang 1 month ago in reply to Yara Al Shami

Prodigy 20 points

It seems the same problem, Thank you very much！

But question number two is what I'm more curious about . Why do SPX/SNX tandem 10R resistors affect SOX waveforms，this have anything to do with the internal circuitry？

0 Yara Al Shami 1 month ago in reply to sirius wang

TI__Expert 7215 points

Hi Sirius,

I believe it is because there is a voltage drop happening across this resistor R172, so by the time it reaches the shunt resistor where the device measures the voltage drop for the CSA the data has already been altered.

Regards,

Yara

0 sirius wang 1 month ago in reply to Yara Al Shami

Prodigy 20 points

Hi，The motor was not connected when we tested this problem.I think this moment of SPA and SNA is similar to being connected together

At this point, the voltage of the SOx is half that of the VREF.I tested the pressure difference between SPA and SNA at the moment of SOA drop, and no voltage change was captured. It seems to have something to do with the internal circuit matching？

0 Yara Al Shami 1 month ago in reply to sirius wang

TI__Expert 7215 points

Hi Sirius,

Do you happen to have waveforms of when SPA and SNA had 10ohm resistors and when they didn't?

Regards,

Yara

0 sirius wang 1 month ago in reply to Yara Al Shami

Prodigy 20 points

Hi，You need the SPA and SNA waveforms as SOA drops？

+1 Yara Al Shami 1 month ago in reply to sirius wang

TI__Expert 7215 points

Hi Sirius,

I discussed this with my team and they agreed that the issue is most likely happening because of the voltage drop across the resistor R172, especially if you aren't seeing this issue when the 10ohms isn't there.

Regards,

Yara

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DRV8353: Drv8353 fault pin drop to 1V when the en signal is enabled