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Original question:

TINA/Spice/LM5155: General Spice Model

LM51551-Q1: PSpice TINA-TI average model

Justinas
Prodigy 120 points
Part Number: LM51551-Q1
Other Parts Discussed in Thread: TINA-TI, LM51551, LM5155EVM-BST, LM5155-Q1

Hello,

I'm working with LM51551-Q1 transient startup model (downloaded from WEBENCH Spicerack) in TINA-TI, simulating boost scheme, similar to the EVM module. Are there any chances of LM51551-Q1 average PSpice model being released/uploaded anytime soon to run AC analysis? 

If not, is it possible to estimate scheme's generated noise in any other way? 

Also, I've done some steady state simulations with WEBENCH, where i got quite messy VOUT signals. On the other hand, results of VOUT in TINA-TI seems too good to me. Could it be that WEBENCH' elements have more parasitic "variables" evaluated in them? I'm attaching snips of sim's below.

Thanks in advance,

Justinas

  • 0
    TI__Guru* 78430 points

    Hi Justinas,

    Thank you for considering the LM51551 for your project. The linear model is on our to do list but currently it is not available yet.

    Regarding your simulations, seemingly the Webench take into account the parasitics especially in the FET and rectifier diode models.  The sim models can help you to get a good start point in your design, and also some quick visualization of your design operation.  However, please always verify and fine tune the design by experiment.

    Thanks,

    Youhao  Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    Prodigy 120 points

    Thanks for your answer,

    LM5155EVM-BST is on the way, but I have some analysis to do before it's here.

    About the FET's parasitics. Does the WEBENCH evaluates all the dynamic characteristics from FET's datasheet (capacitances, charges and etc.)? Or is it only Rdson and the gate charge, mentioned in the WEBENCH app while choosing an alternative part?

    I've found LM5155EVM-BST .tsc simulation file somewhere in TI's website. Transient analysis is running almost fine, except the FET. There're some parametres which "could be changed". But changing them brings no effect on simulation results. Why is that so? I assume that the LM5155-Q1 and the FET in this model are macros with no changes available on them. But there's a line called "SubCKT-(Content)" and the following address is typed there "C:\ELABTRANS_WS\ELABTRANS_DS\Part_Numbers\LM5155-Q1\Active_Work_Sankalp\EXPERIMENTS\TINA-TI\POWERMOS.LIB". Is the missing powermos library causing me these difficulties? 

    I'll add .tsc file.

    Best regards,

    Justinassnvmbv8.TSC

  • 0 in reply to Justinas
    TI__Guru* 78430 points

    Hi Justinas,

    I need to direct this to our experts of the Webench supporting group so they can answer such questions.  

    Best Regards,

    Youhao 

  • 0 in reply to Youhao Xi
    Genius 4910 points

    Hi Justinas,

    Please direct your question to DesignSoft/TINA.  Please use this support page www.tina.com/technical-support/

    Best Regards,

    Atul

  • 0 in reply to Atul_Kulkarni
    TI__Intellectual 2320 points

    Hi Justinas,

    Regarding your below query on WEBENCH simulation results,

    "Also, I've done some steady state simulations with WEBENCH, where i got quite messy VOUT signals. On the other hand, results of VOUT in TINA-TI seems too good to me. Could it be that WEBENCH' elements have more parasitic "variables" evaluated in them?"

    WEBENCH uses relatively more realistic Cout SPICE model than standalone TINA-TI model. The spikes in Vout is usually observed if the Cout model assumes ESL (Equivalent Series Inductance).

    However the standalone TINA-TI model doesn't assume ESL. Hence we are obtaining clean results in TINA-TI.

    Regarding your below query on FET model in TINA-TI,

    Transient analysis is running almost fine, except the FET. There're some parametres which "could be changed". But changing them brings no effect on simulation results. Why is that so? I assume that the LM5155-Q1 and the FET in this model are macros with no changes available on them. But there's a line called "SubCKT-(Content)" and the following address is typed there "C:\ELABTRANS_WS\ELABTRANS_DS\Part_Numbers\LM5155-Q1\Active_Work_Sankalp\EXPERIMENTS\TINA-TI\POWERMOS.LIB". Is the missing powermos library causing me these difficulties? 

    I tried changing the Rdson parameter. It got properly reflected even in simulation results. Follow below steps to change the MOSFET parameters.

    I changed Rdson from 5.7m Ohm to 100m Ohm

    Below are the simulation results with Rdson=5.7m Ohm. The voltage at SW node is 70.33m [= Inductor Current * (Rdson + R6)]

    where Inductor current is 5.13A as shown in below snapshot, R6=8m Ohm (resistor in series with MOSFET)

    Below are the simulation results with Rdson=100m Ohm. The voltage at SW node is 550.83m [= 5.13 * (100m + 8m)]

    Thus it can be concluded that FET parameters are getting properly reflected. Kindly let us know in case you have any further queries.

    Thanks & Regards,

    Harish