DP83822I: VDDIO Timing Requirements and Power-Up Timing

Shotaro Sakai

Part Number: DP83822I

Hello team,

Can you give your knowledge for my support?

I have question on timing requirements of VDDIO. Datasheet says VDDIO should be powered up within 100ms from less than 0.3V.

1. Is there any reason to specify starting from less than 0.3V?
2. What problems can occur if conditions above 0.3V persist for 100ms?

My customer is using two DP83822I (PHY addresses 1 and 2). In rare cases(2/4000), only PHY address 1 is not detected by PHY address scan during initialization at power-on.

They looked VDDIO waveform. The result is 0.3V->1V: 1740ms, 1V->3.15V: 0.5ms.

Best regards,

Shotaro

over 2 years ago

0 Rahul over 2 years ago

TI__Expert 8721 points

Hi Shotaro,

If the power up sequence is not followed, the PHY will not be initialized properly and it will go into an unknown state. We would recommend customers to follow the power-up sequence mentioned in the datasheet.

Regards,
Rahul

0 Shotaro Sakai over 2 years ago in reply to Rahul

TI__Expert 3420 points

Hi Rahul-san,

They are fixing the design but it may takes long time. So they are considering a tentative plan as following.

Reset the PHY when an unknown state occurs and the PHY becomes invisible to the MIDO.

Can the reset pin (18 pin) of the PHY recover properly if an unknown state is entered?

Best regards,

Shotaro

0 Rahul over 2 years ago in reply to Shotaro Sakai

TI__Expert 8721 points

Shotaro-san,

We haven't tested this scenario and not sure if the reset will fix it. I would recommend to follow the specs in the datasheet.

Thanks,
Rahul

0 Shotaro Sakai over 2 years ago in reply to Rahul

TI__Expert 3420 points

Rahul-san,

The below is my customer's request.

Can you try to check if the reset works on this scenario?

Or can you tell me the reason why we are not sure if the reset will fix it?

Best regards,

Shotaro

0 Rahul over 2 years ago in reply to Shotaro Sakai

TI__Expert 8721 points

Shotaro-san,

My wording on unknown state have confused the description.

If the power sequence recommended in the datasheet is not followed, the PHY will not function properly. If the functionality of the PHY is not working, RESET cannot help.

This is the reason we would recommend to follow the power sequence provided in the datasheet.

Thanks,
Rahul

0 Shotaro Sakai over 2 years ago in reply to Rahul

TI__Expert 3420 points

Rahul-san,

Let me double check what you want to say.

If the power sequence is not followed in datasheet, the PHY will not function properly. It means we cannot say that the internal circuit for reset function works normally, right?

Best regards,

Shotaro

+1 Rahul over 2 years ago in reply to Shotaro Sakai

TI__Expert 8721 points

Shotaro Sakai said:
If the power sequence is not followed in datasheet, the PHY will not function properly. It means we cannot say that the internal circuit for reset function works normally, right?

Yes.

Regards,
Rahul

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DP83822I: VDDIO Timing Requirements and Power-Up Timing