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LM2841Y model parameters

JerryLin
Prodigy 180 points

Hello Akshay,

The stuff should be enough. I try to verify the model by TI's LM2841Y Pspice Average Model 

http://www.ti.com/litv/zip/snvm303

The output voltage of original model is 3.3V. In our case, Input voltage is 12V ,output voltage is 3.0V. So we change the feedback resistor R1 from 3.32K to 2.94K. The simulation result of VOUT become very small. For R1=3.32K, it is about 40dB. What is wrong? Can the working condition of Pspice model be changed ?

regards,

Jerry

  • 0
    TI__Genius 15810 points

    Hello Jerry,

    I have actually not worked with the Pspice model at all. I am going to forward your question to the Webench group. The Pspice experts from there will be able to answer your question.

    Regards,
    Akshay 

  • 0 in reply to Akshay Mehta
    TI__Mastermind 39210 points

    Hi Jerry,

    I do not have access to your schematic but this is what I would recommend.

    1. Change the initial condition on VOUT to the VOUT value that you have.

    2. Replace the output cap with a simple capacitor in series with a resistor (ESR). Use the values from your cap datasheet directly.

    3. Run the AC Bode plot simulation. Check the Bias point on the schematic. Does the model give you the correct bias point? 

    4. If you still have issues, please send me your project files (or at least an image of your schematic) and I can have a look.

    Best regards,

  • 0 in reply to Nikhil Gupta (Product Folder Models)
    Prodigy 180 points

    Hello Nikhil Gupta,

    The shematic is just the same as that of  http://www.ti.com/litv/zip/snvm303. Only R1 is changed to 2.94K, and NODESET=3.0

    The simulation loop gain is very small. 

    The project file is attached here.

    0456.LM2841Y_PSPICE_AVG.rar

    best regards,

    Jerry

  • 0 in reply to JerryLin
    Prodigy 180 points

    Hello Nikhil Gupta,

    For the LM2841X Transient Model , how to change the Capacitor Value of COUT? And if I change R1 to 2.94K for Vout=3.0V, and set IC of COUT as 3.0, the simulation stop when the simulation proceed 75%. Pspice displays

    ERROR(ORPSIM-15138): Convergence problem in transient analysis at Time = 1.876E-03.

    These voltages failed to converge:

    V(X_COUT.5) = 468.10uV \ -4.624mV
    V(X_COUT.1) = 469.36uV \ -4.636mV
    INFO(ORPROBE-3185): Simulation paused

    best regards,

    Jerry