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DP83TC812EVM-MC: VDDMAC - 1.8V, EVM not transferring data.

Dharanesh S
Prodigy 60 points
Part Number: DP83TC812EVM-MC
Other Parts Discussed in Thread: DP83TC811EVM, , DP83867IR

Hi,

We are planning to use DP83TC812 100base-T1 RGMII to Automotive ethernet PHY in our design. To validate, we procured DP83TC812EVM-MC and connected it to another EVM from TI DP83TC811EVM to validate with our design. DP83TC812EVM-MC (Master) <--------(2362764-4 (100base-T1 ethernet cable))--------> DP83TC811EVM (Slave)

Q1. Could you please share us the operating temperature of DP83TC812EVM-MC?

Q2. Also, we are planning to use DP83TC812 with Nvidia AGX Orin in our design, and the pin voltage for RGMII pins is 1.8V. When we switched the jumper J3 to switch the voltage level of VDDMAC domain, then we could not get the automotive ethernet link with the EVM. I have shared the observations below for your reference.

1. Normal configuration, with VDDMAC voltage as 2.5V or 3.3V, the DP83TC812EVM-MC works normally without any issue. The Diode D2 and D3 is in on condition indicating a proper link in 100base-T1 line. I have attached the image in normal working configuration for your reference. We have confirmed this working with iperf bandwidth test tool. The MODE led (D8) and CONF led (D9) are in on condition.

2. In configuration with VDDMAC voltage as 1.8V and the MDIO, MDC jumper J14 in mounted condition, the DP83TC812EVM-MC doesn't establish link which can be confirmed with the LED D2 and D3 in off condition. We can also confirm this same with iperf and ping command, that no link is established. In this the MODE led (D8) is on whereas the CONF led (D9) is in off condition. The SQI led (D10) is in on condition, which is indicated as red color.

Upon verification, with the schematics we found that the IO voltage of MDIO, MDC interface given to the DP83867IR (PHY to RJ45) chip is 1.8V whereas other IO's are given as 3.3V due to which the DP83867IR (PHY to RJ45) is in different voltage level compared to the other IC's. So in our understanding the MDIO lines, leads to voltage mismatch compared to other IC's.

3. In configuration 3, we removed the MDIO, MDC jumper J14. VDDMAC jumper is in 1.8V. In this condition, the MODE led (D8) is in on condition also the SQI led (D10) is also in on condition, which is indicated as red color. But the difference in this condition is that, the diode D2 and D3 is in on condition indicating a proper link in 100base-T1 line. So, as per our understanding in this configuration the issue is with MDIO lines in VDDMAC 1.8V. We can also confirm this same with iperf and ping command, that no link is established.

4. In the next configuration, we repeated the same configuration with VDDMAC as 3.3V and we observed the same results. We can also confirm this same with iperf and ping command, that no link is established.

For this issue with VDDMAC 1.8V of DP83TC812, could you please suggest a fix with the EVM with which we could validate in our design?
I have attached the relevant images based on each condition for your reference.

Please let me know if any other additional information is required.
Thanks
Dharaneshwar S

  • 0
    TI__Mastermind 19621 points

    Hi Dharaneshwar

    The temperature rating for the EVM board is NOT the same as the temperature rating for our PHY. It was not built to withstand higher temperatures, nor has it been tested for it. The EVM is purely to prove function.

    I will replicated your setup in lab and see if I can recreate the issue. I will get back to you on Monday, July 17th. 

    Regards,

    Alvaro

  • 0 in reply to Alvaro (Al-vuh-roe) Reyes
    TI__Mastermind 19621 points

    Hi Dharaneshwar,

    I replicated your setup and my results are exactly like yours. Please grant me to the end of the week (07/21) to see if I can find a valid work around solution.

    The problem is as you described, VDDIO for the 812 is 3.3V but the 867 is 1.8V, while the MSP is also at 3.3V.  

    Condition 4 worked, where we disconnected the MDC/MDIO Jumpers. The red SQI light will be on, but we were able to attain link. (If you don't have link, try hitting the reset button or power cycling the board)

    Regards,

    Alvaro

  • 0 in reply to Alvaro (Al-vuh-roe) Reyes
    TI__Mastermind 19621 points

    Hi Dharaneshwar,

    Unfortunately there isn't a way to have the EVM work at VDDIO 1.8V with register reads. As mentioned above, if you remove the MDC & MDIO jumpers the PHY should still be functional, albeit without register read/write access. 

    We have taken note of this issue.

    Regards,

    Alvaro