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SWITCHERPRO / INT POLE CRO... CALCULATION

Ran Feldman
Intellectual 780 points

Other Parts Discussed in Thread: TPS40170

Hi,

Our Customer is using the TPS40170 and he is trying to compensate the part using the SwitcherPro what if Analysis.

A question I got, is what does the Int Ploe Cro..(Crossover?) indicate? How does the SwitcherPro determine it?

Thanks

Ran

  • 0
    TI__Intellectual 1280 points

    Ran,

    I think I can help explain this value in SwitcherPro.  The integrator pole frequency is the frequency of the type III compensation pole/zero of  R1 and C6

    I think it’s really only useful for Voltage mode feedback and Type 3 compensations. This calculation can be found with Fint = 1/(2*pi*R1*C6)

    Below I drew an artificial line that represents this value.  I hope this helps.

     

  • 0 in reply to Heath Gallimore
    Intellectual 780 points

    Hi Heath,

    In the design the TPS40170 is used in the following configuration: 24V input, 5V output, 6A load current. I don't see your schematics so I am not sure which capacitor you are referring to.

    I need some more explanation on this pole. When I change it, it seems that the total gain of the loop changes. I need to understand what is the Int. (Integrator) pole frequency and what does it affect in the loop (mainly I can see gain changes) where does it come from?

    Your arrow indicates the intersect point for the error amplifier gain? before compensation?

    Thanks,

    Ran

  • 0 in reply to Ran Feldman
    TI__Mastermind 28780 points

    Hi Ran,

     

    Thanks for the question. Here's the compensation transfer function used for TPS40170 in terms of the reference designators used in the design.

    (1 + (s * C21 * (R11 + R13))) * (1 + (s * C13 * R4)) / (s * (C13 + C14) * R11 * (1 + (s * C21 * R13)) * (1 + s * R4 * ((C13 * C14) / (C13 + C14))))

    So, in here, the integrator pole frequency is 1/(2*pi*R11*(C13+C14)). As you can see changing these component values will result in a change of gain.

    Please let me know if you need any more inputs on this.

     

    In addition, TPS40170 has been recently integrated into WEBENCH as well. You can access it by following the product folder link where you can see the panel: http://www.ti.com/product/tps40170

     

    Regards,

    Amod