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THS3491: THS3491RGT LTSpice Warning

Chia Hung Lai
Prodigy 110 points
Part Number: THS3491
Other Parts Discussed in Thread: TINA-TI

Hi, I ran the THS3491RGT model in LTSpice & got the following warning message:

WARNING: Less than two connections to node u1:_u113:nref_hi. This node is used by e:u1:_u113:ref_hi.
WARNING: Less than two connections to node u1:_u113:nref_low. This node is used by e:u1:_u113:ref_low.
WARNING: Less than two connections to node u1:_u113:npdz_hi. This node is used by e:u1:_u113:pdz_hi.
WARNING: Less than two connections to node u1:_u113:npdz_low. This node is used by e:u1:_u113:pdz_low.
u1:d_in_clmp: Emission coefficient, N=0.02, too small, limited to 0.1
Direct Newton iteration for .op point succeeded.

Date: Mon Feb 26 19:01:25 2024
Total elapsed time: 0.116 seconds.

tnom = 27
temp = 27
method = trap
totiter = 11
traniter = 0
tranpoints = 0
accept = 0
rejected = 0
matrix size = 243
fillins = 113
solver = Normal
Avg thread counts: 20.0/0.0/20.0/20.0
Matrix Compiler1: 837 opcodes
Matrix Compiler2: 18.19 KB object code size

I understand that LTSpice may not be favorable here but that's how my working environment is. The result seems fine, should I just ignore the warning? or is there a fix I can apply to the model before I run the simulation.

Thanks.

  • 0
    Prodigy 110 points

    Well, I figure out if I do the following changes in the THS3491RGT Spice model, the LTSpice warnings disappear:

    -------------------------------------------------------------------------------------------------------------------------------

    from:

    .model D_IN_CLMP d is=1e-014 n=0.02 rs=1

    to:

    .model D_IN_CLMP d is=1e-014 n=0.1 rs=1

    -------------------------------------------------------------------------------------------------------------------------------

    from:

    *ESHDN SHDN GNDF VALUE = {V(NREF_HI,GNDF)*V(NREF_LOW,GNDF)*V(NPDZ,GNDF)*V(NPDZ_HI,GNDF)*V(NPDZ_LOW,GNDF)}
    ESHDN SHDN GNDF VALUE = {V(NPDZ,GNDF)}

    to:

    ESHDN SHDN GNDF VALUE = {V(NREF_HI,GNDF)*V(NREF_LOW,GNDF)*V(NPDZ,GNDF)*V(NPDZ_HI,GNDF)*V(NPDZ_LOW,GNDF)}
    *ESHDN SHDN GNDF VALUE = {V(NPDZ,GNDF)}

    -------------------------------------------------------------------------------------------------------------------------------

  • 0 in reply to Chia Hung Lai
    TI__Expert 6050 points

    Hi Chia,

    Models are created and tested in the TINA-TI and Pspice environments. There is general guidance on how to import TI models into generic Spice environments, but as you alluded to, the models are not able to be validated in LTSpice and environment specific warnings like these may occur.

    However, it appears that you have found the changes to make the warnings disappear for this simulator environment. I will close this thread. Please feel free to respond to this thread or start a new thread if you have any additional questions.

    Thanks,

    Nick

  • 0 in reply to Nick Nauman
    Prodigy 110 points

    Hi Nick,

    Thanks for the update. I am not an expert in SPICE model, and my "solution" (sort of) is merely a guess. Could TI take a look at my fix above & provide some guidance?

  • 0 in reply to Chia Hung Lai
    TI__Expert 6050 points

    Hi Chia,

    For your first change (n=0.02 to n=0.1), this appears to be a limitation of the LTSpice environment where the coefficient has a minimum size it must be and the model has a smaller coefficient.

    The models we provide are very complex and it is difficult to say what the impact of changing one line of code is. TI's models are designed for use in Pspice and TINA-TI (the simulators we use at TI), but are not necessarily released to be 'drop-in' models for LTspice.  As LTspice is software originally produced by Linear Technologies, we are not able to debug or advise using TI models in LTspice.

    Thanks,

    Nick