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Original question:

TPD2E009: TPD2E009 Spice model

TPD2E009: Spice Model

Elias Tarver
Prodigy 50 points
Part Number: TPD2E009

Tool/software:

It appears that the SPICE model for this device has been requested multiple times in E2E, but I haven't seen one available or published anywhere.  I am trying to use spice models to recreate a suspected failure mode for this device.  

Specifically the potential 'short' of one of the data (D+/D-) lines to +31 VDC relative to the ground used on the component to cause damage.  I believe that it would definitely cause this diode to fail with a first pass of the datasheet, but I wanted to ask and/or simulate this to make myself more sure about that. 

 

  • 0
    TI__Expert 6150 points

    Hi Elias,

    Looks like we had a model created for this device, but it never got published. I faced some errors when opening this file, so I will need to look into this.

    Without a model, I can confirm that a 31V DC voltage short onto D+ will cause the diode to fail, as this will cause the diode to be in the breakdown region for much longer than the diode can tolerate.

    If you are able to provide more information on the interface/application here, I can provide our best recommendation on the protection devices we can offer for a situation like this.

    Best Regards,

    Josh Prushing

  • 0 in reply to Josh Prushing
    Prodigy 50 points

    I am personally not in control of the design of the device itself and cannot update it.  But, this is being used in an RS-485 application.  The Transceiver is a dual RS-422/RS-485  IC, so it has a more limited common mode range than a typical RS-485 IC. 

    A theory of a failure of the device using this diode was proposed to be that 31V was shorted to either D+ or D-.  It was further proposed the short would only damage downstream components with no damage to the diode itself.  This conclusion sounded a bit off to me, so I wanted to check in with TI to see their thoughts on if the TPDE009 would survive this kind of stress on the data lines.

    Combing through threads it appears that someone also has seen transceivers themselves blown out when using this diode in an RS-485 application without any abnormal operation of the bus. So, it seems like using the diode itself isn't the best design choice for RS-585 and that a different failure mode should be attributed to the observed device failure I am debugging.

  • +1 in reply to Elias Tarver
    TI__Expert 6150 points

    Hi Elias,

    Thanks for the additional information here!

    My understanding was that RS-232 and RS-485 typically operated around 12V DC (at least for the input voltage), which would cause TPD2E009 to fail since this is also considerably above the breakdown voltage of the diode. Are you able to provide the IC name so I can confirm the operating voltage?

    Elias Tarver said:
    A theory of a failure of the device using this diode was proposed to be that 31V was shorted to either D+ or D-.  It was further proposed the short would only damage downstream components with no damage to the diode itself.  This conclusion sounded a bit off to me, so I wanted to check in with TI to see their thoughts on if the TPDE009 would survive this kind of stress on the data lines.

    Yes, this conclusion (given my understanding) is incorrect: the diode will fail in this scenario of a 31V short. 

    Is the IC failing without the placement of the ESD diode? What is the cause of this 31V short? 

    Ultimately, it seems that TPD2E009 is not the right fit for your system, but with some additional understanding of the failure condition, we may be able to recommend a different protection device that better suits your needs Slight smile

    Best Regards,

    Josh Prushing

  • 0 in reply to Josh Prushing
    Prodigy 50 points

    My problem is that I have a failure situation and the company that makes the product and did the RMA is providing.... inaccurate evaluations and derivations of what could have possibly actually happened.

    This is making it quite hard to figure out the actual failure mode of the unit as a whole.  I would love to be able to change the design, but unfortunately I am just a lowly engineer trying to build a fault tree with inaccurate inputs.  

  • +1 in reply to Elias Tarver
    TI__Expert 6150 points

    Hi Elias,

    Understood, I wish you the best of luck in debugging the system. 

    If there's anything else I can assist with, please feel free to reach out!

    Best Regards,

    Josh Prushing