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SN74LV1T04: Spice behavioral model for SN74LV1T04 shows VIH=2.5V for VCC=5V in LTspice simulation

Sverre Jakob Alvsvag
Prodigy 10 points
Part Number: SN74LV1T04
Other Parts Discussed in Thread: SN74LV1T02

I downloaded the Pspice behavioral model for SN74LV1T04.

.SUBCKT  Y A B VCC AGND
XU1 Y A B VCC AGND LOGIC_GATE_2PIN_OD_LVC_2i_NOR_PP_CMOS_SN74LV1T02
.ENDS

etc.

It loaded and ran in LTspice without errors or warnings.

I guess the subcircuits it contains are all standard Spice?

The simulation shows that the input have to pass a threshold voltage (VIH) of 2.5V to toggle the output of the inverter (VCC = 5V).

But according to the datasheet is VIH = 2.02 for VCC=5V.

"VCC = 4.5 V to 5.0 V 2.02 2.03"

Why doesn't the model show this behavior which I guess is why it is called a level shifter in the first place? 

  • 0
    TI__Mastermind 26380 points

    Hi Sverre,

    The simulation data is most likely for min typical and max worst cases while the datasheet is with additional tolerance.

    Hence, the device would work for either of both thresholds, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    Prodigy 10 points

    Hi Michael,

    Thank you for the answer. In your video "Solving Voltage Translation Solutions With One Power Rail" the presenter confirms that VIH=2.1V for VCC=5.5V for this family. ( https://www.ti.com/product/SN74LV1T02 ). The data sheet only reports the MIN VIH value: VCC = 5.5 V, MIN VIH = 2.1 V, TYP and MAX values are blank so I don't understand why you mention these in your answer. Are they somehow embedded in the model? I would then have expected a .PARAM statement where MIN, TYP or MAX alternatives are selected. It makes no sense to use anything other than the MIN value for this model as the low VIH is the whole selling point for this circuit. If it doesn't behave like that in the simulation the whole point of using this circuit for level translation is lost. It seems like these thresholds are defined in this statement:


    ESTD_THR VSTD_THR VEE TABLE {V(VCC,VEE)} =
    +(1,0.5)
    +(1.8,0.9)
    +(2.5,1.25)
    +(3.3,1.65)
    +(5,2.5)
    +(6,3)


    In my mind this should rather be (@ 25°C)
    +(5,2.02)

    for VCC=5V.

    Would it be sufficient to modify this TABLE according to the data sheet (7.5 Electrical Characteristics ) to make it behave as the real circuit?

    Best regards
    Sverre Jakob

  • 0 in reply to Sverre Jakob Alvsvag
    TI__Mastermind 26380 points

    Hi Sverre,

    Please note that I have reassigned the thread to the Logic team to further help clarify your LV1T02 concerns, thanks.

    Best Regards,

    Michael.

  • +1 in reply to Sverre Jakob Alvsvag
    TI__Genius 16660 points

    Hi Sverre,

    You are correct in your assessment here. If you modify the table to the following:

    ESTD_THR VSTD_THR VEE TABLE {V(VCC,VEE)} =
    +(1,0.85)
    +(1.8,1)
    +(2.5,1.135)
    +(3.3,1.35)
    +(5,2.02)
    +(6,2.18)

    The device should switch at the appropriate threshold.

    Best,

    Malcolm