DRV8701: RADIATED IMMUNITY FAILURE

Gorka Lorea

Part Number: DRV8701

Hi,

We have designed a DC motor driver PCB and we have used the ref. DRV8701E. Everything was working well with it but when we have gone to do the IEC certificaction of the device we have been surprised because it has failed the radiated immunity test (10V/m field).

Analyzing the problem in depth we have discover that in frequencies between 80 and 84MHz both internal regulators of the DRV8701E falls to 0Vdc. You can see the electronic schematic of the DRV8701 zone

Looking into the datasheet I expected both LDOs to be in parallel as shown in the image

However, falling both at the same time, without falling of Vbus, makes me doubt about it.

- Why dou you think the DRV8701 is failing at those frequencies?

- What can explain that both LDOs fails at the same time?

- Have anybody had any similar problem with this device?

Thank you very much for your support,

Best regards,

over 3 years ago

0 Pablo Armet over 3 years ago

TI__Mastermind 37683 points

Hello Gorka,

We will investigate this issue.

Can you help us with the following questions:

Did the immunity test failed in every device you tested when in the range of 80-84MHz?
Was the device permanently damaged after the test? Does the LDO output remained 0V?

Regards,

Pablo Armet

0 Gorka Lorea over 3 years ago in reply to Pablo Armet

Expert 1620 points

Hi Pablo,

Answering your questions:

1. Yes, we have 5 devices to test and all of the them always fail in the same immunity test. They only fail in those frequencies. If we start the test in 85MHz the device pass the test succesfully. The immunity test starts in 80MHz and finish in 1GHz.

2. No, the device is not permantly damaged. When the disturbance finish or exit these frecuencies the DRV8701 recovers and keep on working correctly.

Regards,

0 Pablo Armet over 3 years ago in reply to Gorka Lorea

TI__Mastermind 37683 points

Gorka,

Thanks for answering the questions.

Did you take any other measurements aside from LDO output you can share with me. I would be interested in seeing the charge pump, VM, and nSLEEP.

Regards,

Pablo Armet

0 Pablo Armet over 3 years ago in reply to Pablo Armet

TI__Mastermind 37683 points

Hi Gorka,

Any updates from your side?

Regards,

Pablo Armet

0 Pablo Armet over 3 years ago in reply to Pablo Armet

TI__Mastermind 37683 points

Hi Gorka,

I have not received an update from you. I will assume the issue has been resolved and will close the thread. You may still reply if further assistance is required.

Regards,

Pablo Armet

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DRV8701: RADIATED IMMUNITY FAILURE