Load regulation of ADM7170

Dear,

I'm trying to simulate the load regulation of the ADM7170 to compare it with figure 4 of the ADM7170 user guide. However, the simulation result is showing a different result for V(out) in function of V(in), the curve in the user guide is going down with increasing input voltage when for the simulation the curve is going up with increasing input voltage. Which one is correct and why?

5722.ADM7170-2.5_loadregulation.asc

Best regards,

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  • 0
    •  Super User 
    on May 5, 2020 11:18 AM in reply to JGillis

    Hello JGills,

    I guess the typical Vout is measured on a test board. The chip has become much hotter at the highest current due to the high power dissipation in this case. When you look at figure 14 in the datasheet, the output voltage typically will drop with higher temperature. Figure 16 shows Vout versus Vin at different currents.
    www.analog.com/.../ADM7170.pdf

    The simulation models normally don't contain any self heating effects due to power dissipation. Also the typical temperature dependency is not modelled. I can't prove this from the SPICE-lines of this model, because the model is encrypted. Maybe somebody from ADI can comment this statement.

    Please be aware in the simulation that the maximum input supply voltage is 6.5V, not 10V as you have simulated.

    By the way the datasheet guarantees +/-0.1%/V.

    Helmut

  • Dear Helmut,

    thank you for your clarification.

    Best regards

  • +1
    •  Analog Employees 
    on Jun 4, 2020 12:12 AM in reply to JGillis

    Hi Jan,

    It's verified that temperature variation is not modeled. You may find that it’s really hard to match exactly the graph shown in the DS from testing the actual part for some parameters. There is a lot of parasitics, changes in parameters and so on, are not taken into account when temperature or frequency goes high.

    Regards,

    Bryan