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ATL431: PSpice model problems...

Jeff Melvin
Prodigy 180 points
Part Number: ATL431
Other Parts Discussed in Thread: , TL431

I get some strange results when "floating" the ATL431 reference.  The image below is a super simplified example.

When the Anode is (almost) connected to ground the Reference and Cathode voltages are correct (as shown on the left, with R1=100kΩ and R4=1mΩ).

When the Cathode is (almost) connected to the high side the Reference and Anode are incorrect (as shown on the right, with R1=1mΩ and R4=100kΩ).

Can you please provide information on how to correct the model so it operates correctly using the configuration on the right?

Jeff

  • 0
    TI__Genius 9375 points

    Hi Jeff,

    I will get a product expert to help you out with this by tomorrow.

    Thanks,
    Abhinav.

  • 0
    TI__Mastermind 19580 points

    Hi Jeff,

    Both configurations are correct. Their is a bug in the ATL431 that causes that model not to work properly in the configuration shown on the right.

    Other models such as the ATL431LI work as intended. Rest assured that if you need to use the schematic in the right, there will be no issues.

    I will pass this information on to see what we can do about the model and fixing this niche use  case.

  • 0 in reply to Marcoo Z
    Prodigy 180 points

    Marcoo,

    I replaced the symbol and model in my "simple simulation" with the ATL431LI and obtained values of 200.0, 166.5 and 163.1V for the "right side" diagram.  This model apparently also has a bug (the cathode-to-anode voltage should drop to ~2V with more than 2.5V from reference-to-anode).

    I'm sure this simple circuit will operate as expected in the real world, but what I'd like to try is certainly not this simple (it just was operating so strangely that I had to revert to this "simple case" to understand what was going wrong).

    The next single step toward my what-if simulations would be adding a resistor between the anode and the junction of R3 & R4... but if I can't understand what is happening here, there is no hope to understanding what happens next...

    I'm hoping you have another suggestion?
    Jeff

  • 0 in reply to Jeff Melvin
    TI__Mastermind 19580 points

    Hi Jeff,

    You are correct, i made a mistake. The ATL431 and ATL431LI spice models have a bug and will not work in this situation. I went through the models and the TL431 is the only one that is working with 2.5V output.

    Internally I feel the device spice has references to GND which is causing issues instead of being anode focused. I will pass on the feedback to see how we can get these models fixed. Currently in the short term, only the TL431 model works properly under the test condition.

    Every model should be working similar to the TL431 behavior.