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Original question:

SN74LVC1G125: Spice Model not showing high impedance state when OE is disabled

SN74LVC1G125: Question about SN74LVC1G125 modified library.

Kazuya Nakai59
Guru 21545 points
Part Number: SN74LVC1G125
Other Parts Discussed in Thread: TINA-TI

Tool/software:

Hello guys,

One of my customers is facing to same trouble as the following thread.
e2e.ti.com/.../sn74lvc1g125-spice-model-not-showing-high-impedance-state-when-oe-is-disabled

Could you please give me you reply for the follow.

I imported the modified library,

3010.SN74LVC1G125.cir

which thread above recommended one.

The symbol shape of modified library was rectangle not triangle. So I thought the import was succeeded.
But the simulation result was not changed.

I think my importing way may be wrong. My importing way was started at "Generate Part" window under "Tools" tag on PSpice for TI.

Is this way correct?

Could I ask you one more question?

SN74LVC1G125 can be simulated on TINA-TI?

Your reply would be much appreciated.

Best regards,
Kazuya.

  • 0
    TI__Mastermind 37845 points

    Hi Kazuya-san,

    I am not sure why it has not worked. I will double check the model. 

    You should be able to use in TINA-TI. All of our models should work in PSPICE or TINA. 

  • 0 in reply to Albert Xu1
    Guru 21545 points

    Hi Albert,

    Thank you very much for your reply.

    I will wait for the result of your double check.

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    Guru 21545 points

    Hi Albert,

    Thank you very much  for your supports.

    Could I ask you another question?
    They are trying to simulate SN74LVC1G125 on TINA-TI.

    But they couldn't find the device in part search window located on right top of TINA-TI window.
    Could you please tell me how to find and place SN74LVC1G125? 
    Is it need to import the logic?

    Thank you again and best regards,
    Kazuya.

      

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 37845 points

    Hi Kazuya,

    The same model should be able to be used in TINA. You may have to convert the file type and import it in. 

  • 0 in reply to Albert Xu1
    Guru 21545 points

    Hi Albert,

    Thank you very much for your supports.

    Did you check SN74LVC1G125 PSpice model? Did the output mode change to 3-state when /EN is high level?

    Thank you again and best regards,
    Kazuya.  

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 37845 points

    Hi Kazuya,

    I did check the model and it works for me. Can you share your schematic? 

    In addition please double check your input signals. 

    /OE = 1: Y = A

    /OE = 0: Y = HIZ

  • 0 in reply to Albert Xu1
    Guru 21545 points

    Hi Albert,

    Thank you very much for your double checking.

    I think correct operation of SN74LVC1G125 is the follow.

    /OE = 0: Y = A

    /OE = 1: Y = HI-Z

    I attached my schematic and waveform.

    In my simulation, Y= low level not Hi-Z when /OE = 1.

    Could you please take a look the attached file?

    Your reply would be much appreciated.

    Thank you again and best regards,
    Kazuya.

    SN74LVC1G125PSpiceSchematic061725.pdf 

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 37845 points

    Hi Kazuya,

    Very sorry, you are correct I typed out the /OE pin wrong, but I tested it the correct way. Please see my below graphs. 

    When I test it out V(y) is on at all times and current across R1 is low. 

    Do note, this is not in PSPICE, as my license seems to have expired. I am working on getting this refreshed. 

    However, different simulators should have the same result. Can you double check if you are using the correct model still? 

  • 0 in reply to Albert Xu1
    TI__Mastermind 37845 points

    Hi Kazuya,

    I talked to one of my coworkers, and it seems like import models to PSPICE are actually not easily done. It has to go through a different validation process. There is a good chance, that the way you imported the model is still the same "bad" model. 

    The simulator I used was QSPICE, which is a free software that is based off LTSPICE. If able, you can try to simulate through QSPICE and see if you still get the wrong results. 

  • 0 in reply to Albert Xu1
    Guru 21545 points

    Hi Albert,

    Thank you very much for your strong supports.

    In my side, I got same result as the waveform I attached to the previous post
    when I used the original SN74LVC1G125 model (the symbol shape is triangle) in PSpice for TI.

    I'd like to confirm the following.

    "The original SN74LVC1G125 model (the symbol shape is triangle) in PSpice for TI operates correctly"

    Is this correct or not?

    If this is correct, then there must be something wrong with our settings.

    Do you have any idea where the mistake might be?

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 37845 points

    Hi Kazuya,

    I believe the only way for the to be resolved will be on the TI side. 

    I will have to make a ticket to update the model and have our modelling team eventually upload the correct model to the PSPICE library. It seems that you cannot locally upload a model to PSPICE, it has to use a model from the library. 

    In the mean time, have you tried TINA or QSPICE modelling, since as you can see in my screenshots, in QSPICE, the model does work correctly. 

  • 0 in reply to Albert Xu1
    Guru 21545 points

    Hi Albert,

    Thank you very much for your reply.

    I understood that TI original SN74LVC1G125 model doesn't work on PSpice for TI.
    Do you have any plan to fix the model bug?

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Genius 12871 points

    Hi Kazuya,

    Albert has submitted the ticket for this model to be fixed.