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SN6505B: LTSpice Simulation with SN6505B

Intellectual 795 points

Replies: 18

Views: 282

Part Number: SN6505B

Hello,

I'm trying to simulate a simple push-pull converter using the transformer driver SN6505B.  I downloaded the Pspice model from 

https://www.ti.com/product/SN6505B#design-development

I imported the .lib file into LTSpice.  However, I'm getting very weird results and LTSpice is taking forever to solve.  Am I doing something wrong in my simulation?  Or is there a problem with TI's Pspice model for this part?

I've attached my LTSpice model, as well as a screenshot of my model.  Any help would be greatly appreciated.

Thanks,

Kevin

SN6505B Simulation.zip

  • Hi Kevin,

    Thanks for posting to E2E! We do not support the creation of models for use with LT Spice: our models are created for use in TINA-TI, and PSpice. However, the SN650x models should work in LTSpice.

    It's possible the inductors are not behaving as a transformer normally would since they look like coupled inductors. Please attempt to use the P-SPICE for TI SN6505B reference models linked here, if possible. Otherwise, please analyze the SN6505 model in a configuration as shown in the test circuit excerpt below from SN6505 datasheet shown, and ensure the D1/D2 switching waveforms operate as expected:



    Please let us know if this advice is helpful.


    Thank you, and have a great weekend,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Manuel,

    Thank you for your reply.  The simple test circuit is not working in LTSpice either.  Unfortunately I do not have Pspice and it is not free.  So maybe TINA-TI is my best option right now.

    I also downloaded your TINA-TI model SLLM322.TSC for this part.  That model is working.  However, is it possible to edit the transformer parameters?  (I'm not seeing any way to do that and it's telling me the macro is encrypted.)

    Or is there a way in TINA-TI to build my transformer that is center-tapped on both sides?  In TINA-TI's transformer options on the top toolbar, I'm only seeing an option to add a transformer that is center-tapped on one side.

    Thanks,

    Kevin

  • In reply to Kevin Bachovchin:

    Hi Kevin,

    You're welcome! TI does offer a free version of PSpice, found here, and I do recommend using that software moving forward.

    Unfortunately, the transformer is the trickiest part of SN6505 simulations because the parameters in both TINA-TI and PSpice for TI designs are locked, as you mentioned, and there is not an ability to create center-tapped push-pull transformers.

    Our recommendation is to import simulation models of the transformer part number you are interested in using. These can be requested from transformer vendors directly, and might also be compatible with 3rd party Spice programs.

    Which parameters are you looking to evaluate in SN6505B systems?


    Thank you,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Manuel,

    Thanks for your reply.  I'm just looking to verify correct behavior of my circuit and to make sure all components are rated sufficiently.

    I requested a PSpice for TI license and I'm awaiting approval.  Overall, between TINA-TI and PSpice for TI, which one do you recommend?

    In LTSpice, it is possible to model a center-tapped transformer on both sides by declaring SPICE for mutual inductance between any number of inductors as described in:

    http://web.cecs.pdx.edu/~tymerski/ece222/How%20to%20create%20a%20transformer%20using%20LTSpice.pdf

    Is any similar feature possible in PSpice for TI or TINA-TI for modelling dual center-tapped transformers?

    Thanks,

    Kevin

  • In reply to Manuel Chavez:

    Manuel,

    I'm trying to do what you suggested and import the simulation model from the transformer I'm using (Wurth Electronics 760390014).  The SPICE file for this transformer is located here:

    https://www.we-online.com/web/en/electronic_components/produkte_pb/bauteilebibliotheken/ltspice/ltspice.php

    However, when I go to import the .lib file into TINA-TI, I get the following error: "Error loading library. File is Empty!"

    The .lib is encrypted, but it works fine to import into LTSpice.  However, I can't import it into TINA-TI.

    How I can simulate a simple circuit with TI transformer driver SN6505B and Wurth Electronics 760390014 transformer?  

    Thanks,

    Kevin

    Thanks,

    Kevin

  • In reply to Kevin Bachovchin:

    Hi Kevin,

    Thank you for following up! PSpice for TI is TI's newest simulation software, so we are looking to make this the go-to choice for our customers and development efforts over TINA-TI. There is an ability to couple components in PSpice for TI (Place menu > PSpice Component... > Passives > Coupling), although I'm not familiar with coupling inductors for this purpose.

    The error message observed from using the 760390014 model is likely from the model being encrypted and compatible with LTSpice only. This model will need to be an unencrypted version to be compatible with PSpice for TI, so I will check for unencrypted model to share with you; meanwhile, I do appreciate your patience.

    Regarding the components in your simulation screenshot, the 1N914 diode is rated for 300mA max forward current. This won't be a problem if your isolated loads will be much smaller, but I do encourage you to use Schottky diodes recommended in the SN6505 datasheet like MBR0530 or RB168MM-40. Transformer 760390014 is a commonly-used transformer with our transformer-driver parts, and it is compatible with SN6505B.

    I will follow up within 1 - 2 days regarding the transformer model, and please let me know if you have additional questions meanwhile.


    Thank you,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Hi Kevin,

    I confirmed with Wurth: they do not have PSpice or unencrypted simulation models available for their parts. Other transformer vendors may have these models, but it may be most fruitful to analyze an SN6505B EVM in your lab setup. If you'd like, we can arrange delivery of an EVM via email or PM.


    Best,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Manual,

    While I'm not able to import the transformer model into TINA-TI, I am able to import their encrypted model into LTSpice.  Will I be able to import an encrypted model into PSpice for TI?

    I submitted the request for PSpice for TI on Friday after your reply, but I still have not received authorization for PSpice for TI.  How long does that typically take?

    Thanks,

    Kevin

  • In reply to Kevin Bachovchin:

    Hi Kevin,

    I understand the Wurth transformer models are designed for LTSpice, so problems aren't expected when importing the transformer model into LTSpice. Unfortunately, this model is encrypted, so it will not be compatible with PSpice for TI as these programs handle certain model files differently.

    Regarding the PSpice for TI download approval, this can take 24-48 business hours, so it's possible you do have an approval email in your junk email folder or you may already be able to visit the PSpice for TI download website and access the download files. Otherwise, I expect the approval email to be sent by tomorrow morning at the latest.


    Thank you,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Hi Kevin,

    Please let me know if you are interested in an SN6505B EVM, and we can coordinate the shipment offline. This is likely the simplest way to accurately analyze an SN6505, and we will be glad to continue providing technical assistance should you have any questions using the physical device and system.


    Thank you for your time,
    Manuel Chavez