DP83848J: Risk of damage when RBIAS is 4.87ohm

Shinichi Inoue

Guru 22301 points

Part Number: DP83848J

Dear Specialists,

My customer wrongly connected 4.87ohm resistor to the RBIAS(20pin). It should be 4.87kohm.

In this case, what kind of impact is expected.

We are concerned that the resistance of the RBIAS pin is lower than expected and there is a risk of damage.

I appreciate your great help in advance.

Best regards,

Shinichi

over 4 years ago

+1 David Creger over 4 years ago

TI__Mastermind 28082 points

Hi Shinichi,

This configuration has not been tested, but there is a possibility it could cause damage. Please switch the resistor back to the 4.87kohm and replace the device if necessary.

Thanks,

David

0 Shinichi Inoue over 4 years ago in reply to David Creger

Guru 22301 points

Hi David,

Thank you for your reply.

I sent your suggestion to the customer and has an additional question.

Could you please advise.

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To consider the answer and other threads about RBIAS,

RBIAS speculated that it was determining the reference voltage for sending and receiving data.

In our board, although DP83848 is mounted on the board, the Ethernet circuit is not used (because it is an option), and the cable is not connected.

Therefore, there is no change in input / output, and we consider that there is no effect on the device.

We think that the worst case you mentioned is for all cases when a resistance value other than the specified one is connected.

Our conclusions are as follows, are these correct?

1) Since the reference voltage is abnormal, the transmission / reception judgment criteria will change, and normal judgment cannot be made.

2) Since the operation cannot be guaranteed, if it is operated, it may lead to the failure of the device in the worst case.

3) At our company, DP83848 is mounted but not used, and the cable is not connected. There is no risk of damage in this state.

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I appreciate your great help and cooperation.

Best regards,

Shinichi

+1 David Creger over 4 years ago in reply to Shinichi Inoue

TI__Mastermind 28082 points

Hi Shinichi,

I agree with your conclusions. There is no way for us to know whether the device is damaged, so you can replace the devices proactively or continue using it to see if operation is still normal, but we cannot guarantee normal operation.

Thanks,

David

0 Shinichi Inoue over 4 years ago in reply to David Creger

Guru 22301 points

Hi David,

Thank you for your reply.

I'll share your answer with the customer.

It's strange to me the device is mounted on a board and doesn't use any circuits, but the customer will be relieved that there is no risk of damage.

I appreciate your great help and cooperation.

Best regards,

Shinichi

0 David Creger over 4 years ago in reply to Shinichi Inoue

TI__Mastermind 28082 points

No problem

-David

0 Shinichi Inoue over 4 years ago in reply to David Creger

Guru 22301 points

Hi David,

The customer satisfied with your suggestion.

Let's close this thread.

I appreciate your great help and cooperation.

Best regards,

Shinichi

0 David Creger over 4 years ago in reply to Shinichi Inoue

TI__Mastermind 28082 points

Good to hear. Closing this thread.

Thanks,

David

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DP83848J: Risk of damage when RBIAS is 4.87ohm