• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 31 subscribers
  • Views 809 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ESD Ethernet level of voltage protection

Vladimir Aparin
Expert 2610 points
Other Parts Discussed in Thread: TM4C129ENCPDT, TPD4E1U06, TIDA-00226

I'm designing schematics for TM4C129ENCPDT with Ethernet.
I need an ESD protection.

I found some design notes:
In TM4C129X System Design Guidelines SLVU2.8-4 has using  with ESD level of 2.8 V.
In TIDA-00226 TPD4E1U06 has unsing with ESD level of 6.5 V.
But Ethernet requires only +1, -1 V  
One more thing - I can't found absolute maximum level of voltage on Ethernet pins in TM4C129. So I think It's like on other MCU pins - 3.3 V.
So it's very strange, that all Ethernet ESD protections from TI has DC Breakdown Voltage much more that Ethernet voltage and much more that absolute maximum voltage for MCU pins.

But now I have theree questions.
1. What is the absolute maximum level of voltage on Ethernet pin for TM4C129x?
2. What level of ESD required for Ethernet?
3. Where ESD protection have to be placed - between MCU and transformer or between transformer and 8P8C(RJ-45) connector?

  • 0
    TI__Mastermind 31600 points
    Vladimir,

    I have moved your post to the TM4C Microcontrollers forum so that it can get visibility by the experts in these devices.

    Patrick
  • 0
    TI__Guru**** 244380 points
    Hello Vladmir,

    Please refer to the System Design Guidelines for TM4C129

    www.ti.com/.../spma056.pdf

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Guru 27285 points

    Amit Ashara said:
    Please refer to the System Design Guidelines for TM4C129

    Hi Amit, Good shoot. Good reference forever to follow AS IS.

     I remember all was on guide I read too and well addressed, but in a few word:

     ESD on Ethernet has two purposes, prevent overvoltage from both differential and common mode, differential and slow common mode  can be best prevented at primary.

     When overvoltage is  primary it can saturate transformer and do cross talk spikes too so at secondary side of transformer  single active network can provide full protection to common inducted too. Primary overvoltage due to ESD show this event is not so frequent due to nature of cable.

     Common mode instead cross all cable and by capacitive coupling transfer to secondary too, preferred way of ESD so is secondary and ESD RC on primary, this prevent all, guidelines show at secondary active only and it is enough for a regular moderate non harsh environment where TIVA is targeted for, some care if Automotive has to be added.

     @Amit, when we can apply some ESD protection to forum too? ;)

  • 0 in reply to Amit Ashara
    Expert 2610 points

    Hello Amit.
    As you can see in topic I seen this document.
    Why in new design for industrial TIDA-00226 has using another schematics of ESD protection? ESD voltage in new design is higher too. Why?

    And in your answer is no information about maximum level of voltage on Ethernet pins. Where I can get this information?

    Regards,
    Vladimir

  • 0 in reply to Vladimir Aparin
    TI__Guru**** 244380 points
    Hello Vladimir,

    The choice of ESD protection is dependent on test, application and cost. Note that one device has Power Line Protection and other does not

    1. What is the absolute maximum level of voltage on Ethernet pin for TM4C129x?
    >> The maximum voltage on any pin is limited by the parameter VIN_GPIO in the data sheet of the device. Do note that this is the worst case and has reliability impact if operated over in this range. How much impact if the IO is at 4V for 10% of the time and so on cannot be quantified.

    2. What level of ESD required for Ethernet?
    >> Both devices are for Ethernet and it is better to keep it lesser than the VIN_GPIO but more than the min operating voltage

    3. Where ESD protection have to be placed - between MCU and transformer or between transformer and 8P8C(RJ-45) connector?
    >> This is mentioned in the System Design Guidelines. it can be placed between MCU and Transformer or between Transfer and RJ45


    Regards
    Amit
  • 0 in reply to Amit Ashara
    Prodigy 10 points
    Hi Vladimir,

    It seems that there may be an inconsistency for the maximum voltage input to the ethernet pins to the TM4C129X. In the data sheet it specifies the maximum voltage for any pin is 4V. However in the ethernet reference designs the lines are biased at 3.3V at the transformer. Meaning the signals can swing +/- 1V at the 3.3V line which puts the peak of the signal at 4.3V.

    So this either means the reference design is incorrect or the datasheet is?

    Reference design link:
    www.ti.com/.../spmu365a.pdf