TLK105L: TLK105 questions,pls confrim

Hello Kailyn,

Is it possible for you to share schematics and the part number for the magnetics used on your board? Is it exactly same as the IDK?

-Regards,
Aniruddha

Hi Aniruddha,

We have the same schematic for AM437x IDK, TLK105L for both ethercat IN/OUT port and another MII port for ethernet. We try also to connect one ethercat port of AM437x IDK board to a LAN while board is power off, same result, our LAN detects loop connection. We tried ethercat boards from Beckhoff but no loop connection detected.

Regards,

Noel

Hi Noel,

Have you tried using a magnetic with a CMC?
It has been identified that a CMC will prevent this power-down link issue from occurring.

Alternatively, can you replace the TLK105L with the DP83822I? The DP83822I is our new 10/100Mbps PHY for TLK replacement.
It does not have this issue.

Kind regards,
Ross

Hi Ross,

Yes, that is exactly what we did, fortunatey DP83822I is pin-to-pin compatible with TLK105. No issue so far. But our customer would like to know if the TLK105L behavior is a natural or a bug? And for the boards that are already in the field, what are other ways to remove the loop detection when power is not applied other than replacing the PHY.

Regards,

Noel

Hi Noel,

If you do not have a magnetic with a CMC, there is possibility to see this issue with the TLK105.
We require that a CMC be included to prevent pulses from propagating into the IC RD pins and out through the TD pins when the device is not powered. Another option is to add common mode termination to the board.

Kind regards,
Ross

Hi Ross,

How do we use this magnetic with CMC? Is it externally connected? Do you have an application notes for this workaround?

Thanks,

Noel

Hi Noel,

You would have to select a transformer that has an integrated CMC. In this case, you have a PCB already built so you would look for a compatible footprint. You should see the CMC in the schematic of the circuit in the transformer datasheet.

As an example, see the common mode windings in sheet 2 of the HX1198FML from Pulse:
productfinder.pulseeng.com/.../HX1198FNL.pdf

Best Regards,

Hi Rob,

We are using below connector with integrated magnetics.

http://www.image.micros.com.pl/_dane_techniczne_auto/z%20lpj0011abnl.pdf

Based on your reference, i think the schematic are somewhat similar. What do you think?

Regards,

Noel

Hi Rob,

So you mean, this magnetics does not comply with TLK105 but is OK with DP83822? Still, it does not answer my original question regarding the behavior of the TLK105, is it a bug somewhere?

It is ok to change the PHY device, but our customer needs answers for this.

Thank you,

Noel

Hi Noel,

Lets clarify.  You are having the problem where the TLK105L is off but connecting a cable causes a link up condition to occur.  You have the magnetics in your design that you sent a link to.

In the magnetics you sent a link to, the CMCs are on the cable side of the device meaning the chokes appear between the transformers and the RJ45.  When using the chokes to limit the self-link occurences with 100base-tx PHYs, the CMCs should be placed between the magnetics and the TLK105L.

Regards,