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LM5122: LM5122

Cedrick Biellmann
Prodigy 150 points
Part Number: LM5122


Hello,

I would like to know if the voltage ramp added to inductor current is as follow:

Where Tsw is the frequency of the DCDC and Vslope is the voltage at Tsw : 

Thank you 

Biellmann Cedrick

  • 0
    TI__Guru 67130 points

    Hello Cedrick Biellmann,

    Yes, see details here: LM5122 datasheet | Slope Compensation

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 150 points

    Hello,

    It's not clear in datasheet. I' m just want to know if at Tsw, Vslope is calculated like the formula I show you.

    I remark too when I change the ambient temperature in Tina, the model works only at 27°C. Is the model work only at 27°C and not for example at 85°C?

    CB

  • 0 in reply to Cedrick Biellmann
    TI__Guru 67130 points

    Hello Cedrick,

    Yes, the formula calculates the slope of the added slope compensation. But please check out above section for the details.

    The model is not modelling temperature as far as I know. What happens when you change the temperature?

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 150 points

    Hello,

    When I change the temperature to 85°C for example, my DCDC converter doesn't work (No current, no output). When I use PSPICE, it tells me that there is a problem with the saturation current of the diodes D11, D1,...(The IS parameter adjusted for temperature has exceeded its maximum limit probably because the N parameter is too small). So I think that the model works only at 27°C. It's a problem for me because I need to do some worst case calculation according temperature.

    Thank you

    CB

  • 0 in reply to Cedrick Biellmann
    TI__Guru 67130 points

    Hello Cedrick,

    Be aware that no model can replace real measurements, so I would recommend using measurements at the different temperatures and then add margin and base the worst case calculations on the real measurements.

    Best regards,
    Brigitte

  • 0 in reply to Cedrick Biellmann
    TI__Mastermind 30830 points

    Hi Cedrick,

    From PSpice simulation side, I can add the following comments:
    Even though PSpice for TI is capable of temperature sweep measurements and Monte Carlo analysis, the simulations will not be accurate or might even lead to errors like you experienced.
    This is because some of the internal components are simplified and do not include all temperature ranges and tolerances.
    The notes in each model should list the features that are not simulated. This includes overtemperature protection for all our models.

    Best regards,
    Niklas