DP83849I: LED_LINK intermittent reversed polarity

Pavel Katkov

Part Number: DP83849I

The part works fine except one issue.

LED_LINK_A/AN0_A and LED_LINK_B/AN0_B once in a while detect wrong polarity and would be OFF when the LINK is established and shortly blink ON on activity. When the cable is disconnected the LED would be ON. With s/w or h/w reset or power cycle it usually is back to normal.

The pins are connected to LED, 150 Ohm Resistor to VCC 3.3VDC. Datasheet shows 165 Ohm but 150 should be even better for the right polarity detection.

Any suggestions?

Thank you

over 8 years ago

0 Rob Rodrigues over 8 years ago

TI__Mastermind 19780 points

Hi Pavel,

Do you have a pull-up resistor from LED_LINK_A/AN0_A and LED_LINK_B/AN0_B to VCC in parallel with the LED and resistor?

Can you share a schematic?

Best Regards,

0 Pavel Katkov over 8 years ago in reply to Rob Rodrigues

Prodigy 30 points

Hi Rob,

No I do not have pull-up resistors in parallel. They were not on a reference design that I was using. Are they necessary for correct detection? What value?

I do not see how I can share the schematic. Paste of a picture does not seem to work. Please suggest.

Thank you

Pavel

0 Aniruddha Khadye over 8 years ago in reply to Pavel Katkov

TI__Mastermind 18425 points

Hello Pavel,

When typing your reply, please click on the 'Use rich formatting' link at the bottom right corner of the reply window. In the new window you will have option to Insert Media, Insert File, or Paste from Word.

-Regards,

Aniruddha

0 Pavel Katkov over 8 years ago in reply to Aniruddha Khadye

Prodigy 30 points

Thank you Ahiruddha,

Here are relevant parts of the schematic:

This is PHY connections.

These are Pulse RJ45 connectors with integrated magnetics and LEDs:

Rob, please let me know if you see something that might cause the problem.

Thank you

Pavel

Interface

Interface forum

DP83849I: LED_LINK intermittent reversed polarity