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SN74LV1T34: Spice Model VIH Not Aligning with Datasheet

Drew Nakamura
Prodigy 10 points

Part Number: SN74LV1T34

Hi,

I ported the spice model for SN74LV1T34 into LTspice, but was noticing a discrepancy on the VIH compared to the datasheet. For a 4.4V supply, I'd expect VIH to be <1.8V, but in the simulation it's actually closer to 2.2V. Is this intended? Please let me know. I'm having troubles attaching the screenshot, but it shows the output only starting to rise once Vin = 2.2V.

Thanks!

  • 0
    Prodigy 10 points

    Adding that it looks like this is how the model is actually defined based on the Schmitt trigger input select points:

    +(1,0.5)
    +(1.8,0.9)
    +(2.5,1.25)
    +(3.3,1.65)
    +(5,2.5)
    +(6,3) 

    based on these points we'd end up at (4.4, 2.2). 

    Figure 8-3 and the VIH table from the electrical characteristics to not align with these either. Even with the worst case values from the characteristics, I'd expect (4.4, 1.97).

    Please let me know!

  • 0 in reply to Drew Nakamura
    TI__Mastermind 40210 points

    Hello Drew,

    LTSpice is a software supported by ADI and unfortunately I won't be able to assist much here. 

    Are you taking the SN74LV1T34 IBIS model and converting it to LTSpice?

    Regards,

    Josh