DP83620: Bus Contention while using with TS3L4892RHHR

Amarnath Murugadass

Part Number: DP83620

Currently in our design we are having a two Ethernet RJ45 ports with Ethernet PHY - DP83620 along with LAN switch TS3L4892RHHR in our design.

We are planning to use this TS3L4892RHHR part as a pass through switch (connecting two RJ45 port) when the power to both Ethernet PHY power is not provided/failed and the 100Base TX signal will be looped back through the other RJ45 port by default hardware configuration of the select pin.

During normal condition the LAN switch will be used to connect the RJ45 ports with the respective Ethernet PHY.

During the power down of the Ethernet Phy will there be any issue for the Ethernet PHY and the LAN pass through switch like bus contention or current leakage through Ethernet PHY as the switch will be powered on.

Any precaution required to be taken for the above condition considering the Eth PHY will be turned off condition and LAN switch will be powered On with the channel selected to connect both the RJ45 port.

over 4 years ago

0 Adrian Kam over 4 years ago

TI__Expert 5425 points

Hi Amarnath,

If you use magnetics as shown in the system diagram, then you should not have to worry about bus contention or current leakage. The magnetics should isolate the ethernet PHY from the rest of your system.

Regards,

Adrian Kam

0 Amarnath Murugadass over 4 years ago in reply to Adrian Kam

Intellectual 480 points

Hi Adrian,

The switch would be between the Ethernet PHY and the RJ45. Also we are planning to use an RJ45 with an integrated magnetics.

So in our design we want to ensure when there is no power to the Ethernet PHY; it shouldn't draw any leakage current from the Switch which might affect the switch or phy.

Our current assumption is as the Switch is analog and doesn't drive any current if the particular channel is not selected.

Can you confirm our understanding

Thanks & Regards,

M Amarnath

0 Cecilia Reyes over 4 years ago in reply to Amarnath Murugadass

TI__Genius 9920 points

Hi,

Adrian is out of the office right now due to observance of US holidays. He'll get back to you when he returns. Apologies on the delayed response

0 Adrian Kam over 4 years ago in reply to Cecilia Reyes

TI__Expert 5425 points

Hi Amarnath,

Your understanding is correct. The Ethernet PHY should not draw any leakage current when it is turned off, so the switch and the PHY should be safe.

Regards,

Adrian Kam

0 Amarnath Murugadass over 4 years ago in reply to Adrian Kam

Intellectual 480 points

Hi Adrian,

What will be the status of the Ethernet PHY TXD+/TXD- and RXD+/RXD- pin during power off condition? Also what is the maximum allowable current through these pins?

Regards,

M Amarnath

0 Adrian Kam over 4 years ago in reply to Amarnath Murugadass

TI__Expert 5425 points

Hi Amarnath,

It seems Gerome is handling this questions on the thread below:

https://e2e.ti.com/support/interface/f/138/t/967839

As stated on the other thread, it will take a couple of days for him to investigate the matter. Since this is being answered on another thread, I will close this one.

Regards,

Adrian Kam

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DP83620: Bus Contention while using with TS3L4892RHHR