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SN74AHC14: SPICE model issues for SN74AHC14 and similar candidate devices, unable to compare

Marko Dukši
Prodigy 30 points
Part Number: SN74AHC14
Other Parts Discussed in Thread: SN74HCS04, SN74LV14A, SN74LVC14A

Tool/software:

Dear TI experts, as it stands now, I currently have no trust in SPICE models provided for TI parts. Please can you elaborate on the following:

1) The SPICE model on this page: https://www.ti.com/product/SN74AHC14#design-tools-simulation has this on line 118 in SN74AHC14.cir:

.PARAM MAXICC = maxICC

which brakes the model since maxICC is just a spaceholder.

2) SPICE models for other candidate devices I am trying to compare it against have the following equivalent lines:

SN74HCS04.cir (line 118): .PARAM MAXICC = 0.0009

SN74LV14A.cir (line 118): .PARAM MAXICC = 0.032

SN74LVC14A.cir (line 124): .PARAM MAXICC = 0.032

which makes the models not broken but also not exactly credible. Datasheets are not unified in what parameters they convey and how, so they do not provide the basis for direct comparison between those parts.

Therefore, I am trying to simulate the shoot-through current during a switching event triggered by a slow input. I get some nonsensical values. Powered by 3.3 V, I get peak currents of 1.54 mA (which actually seems about right), but also 37.6 mA and 51.4 mA (on the rising output edge) for those three devices, U1, U3 and U4 respectively (U2 is AHC and is excluded since it brakes the simulation):

SPICE Transient

The whole point of trying to simulate it is to be able to identify a device which will consume the least amount of power in my particular application scenario, both statically and during switching events. However, I cannot simulate the AHC device at all because of its broken model, while the results from the other three models do not instill confidence.

Can you please fix these models so they would be accurate at least relative to each other? Thank you so very much! Best regards,

Marko Dukši

  • 0
    TI__Mastermind 40615 points

    Hi Marko,

    Our team will look into these models. 

  • 0 in reply to Albert Xu1
    Prodigy 30 points

    Hi Albert Xu1! Regarding the broken model with undefined MAXICC parameter (for the  AHC device), I had to move on with the models that were not obviously broken. The three previously reported to exhibit suspicious shoot-through Icc values are still being compared but I added one more from the AUP family. The results of DC sweep simulations still make no sense. Here are the simulated curves for all four devices using PSpice models provided by TI, simulation parameters, recorded min and max values for each curve and the schematic overview:

    Spice DC sweep results

    Also, as a direct comparison, the HCS device actually has the curves depicted in the Figure 6-3. on the page 7 of the datasheet:

    https://www.ti.com/lit/ds/symlink/sn74hcs04.pdf

    which disagree with simulation results by an order of magnitude.

    I hope this helps your team in troubleshooting the models. Best regards,

    Marko Dukši