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TPD4E1B06: TPD4E1B06 clamping voltage for Ethernet application and MCU operating at 3.3V

Charles Tsai
Guru**** 187006 points
Part Number: TPD4E1B06
Other Parts Discussed in Thread: ESDS314, STRIKE, ESDS304

Hi Team,

  According to the datasheet the clamping voltage can be more than 10V. We have a customer who currently uses the  TPD4E1B06 as a protection diode which sits between the Ethernet RJ45 connector and the MCU (with built-in Ethernet PHY) operating at 3.3V. Please reference this post if you are interested to read the details. https://e2e.ti.com/support/microcontrollers/other/f/908/t/956641.  It is a bit lengthy.  We are suspicious the high clamping voltage may have allowed voltages higher than what the MCU is designed to tolerate and hence damage the device in the events such as ESD. The question to ask is if the TPD4E1B06 is suitable for the application to interface with the MCU. What will be the recommended part to use for such application?

  • 0
    TI__Expert 8486 points

    Hello Charles,

    If the MCU operating voltage is 3.3 V, I would recommend a part with a lower Vrwm to get a lower clamping voltage. I would recommend the ESDS314. It's a 4 channel part with a 3.6 V Vrwm and a much lower clamping voltage (5.5 V @ 16 A (8kV ESD strike)). Would this be suitable for your customer's application?

    Regards,

    Matt Smith

  • 0 in reply to Matt Smith3
    Intellectual 420 points

    Hi Matt

    The trouble is I am not that familiar with Ethernet or ESD protection, and had assumed I could just use the part in TI's design guidelines for the TM4C1294 which now is appearing to be not the case.

    I had been looking at the ESDS304 as a possible solution, and it looks like the ESDS314 is just a beefier version.

    Besides the potential for damage from ESD, which I understand to be short high energy spikes, one if the things we are seeing when probing the Ethernet lines is a gradual rise in voltage, these ESD diodes are going to do their best to limit that to 3.6V, do you think that will just be masking a different issue or would you guess that this rise is caused by ESD events.

  • 0 in reply to Hugh Powell
    TI__Expert 8486 points

    Hi Hugh,

    If you'd like to learn about ESD protection, I'd start with our 5 part blog series found at the top of our training page. We also have video series and white papers that go in more detail on that page as well. One of my favorite guides is the System Level ESD Protection Guide. 

    Regarding the situation you're showing me with the gradual voltage rise, is the oscillation normal, or is this an induced event? The voltage rising to about 4.8 V (peak) seems very odd if the normal working voltage is only 3.3 V. 

    Regards,

    Matt Smith

     

  • 0 in reply to Matt Smith3
    Intellectual 420 points

    Hi Matt

    I will have a look through the recommended resources.

    This whole issue has come about as per my original thread. Long story short I am having issues with the ethernet PHY on my custom board degrading over time for unknown reasons.

    As part of debugging we recorded the signal lines to the PHY and saw the above data, I cant find any other traces of what PHY signals for 10Base-T Ethernet should look like, they only ever seem to show the differential.

    Of note the level of these signals seems to float up above 3.3V by a significant amount ending up outside the recommended operating conditions of the IO pins.

    Without further information I don't know if this is expected behavior or what is potentially damaging my chip, or if it is being damaged by seperate ESD events, noting that by my reading the ESD protection option ( TPD4E1B06) I used from the design guideline doesnt seem to be appropriate due to its high clamping voltage.

  • 0 in reply to Hugh Powell
    TI__Expert 8486 points

    Hi Hugh,

    Thanks for the clarification, and yes, I agree that the TPD4E1B06 clamping voltage would be too high for your needs. I highly doubt that multiple ESD events are happening to create this over-voltage situation. However, if you find out that the issue has to do with ESD please feel free to respond to this thread again. 

    Regards,

    Matt Smith