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TPS53317 Compensation network

geoffrey wall
Prodigy 30 points
Other Parts Discussed in Thread: TPS53317, TPS51317

I want to use TPS53317 in my design.

In the "VTT Application" figure on page 8 of the data sheet is shown an example schematic which uses the part.

In this schematic is a compensation network.

The only discussion on how to choose the compensation network is on page 11 of the data sheet:

"The value of the resistor (RC) can be calculated using the desired unity gain bandwidth of the converter, and the
value of the capacitor (CC) can be calculated by knowing where the zero location is desired."

This is not enough information for me to know what value to use for the resistors and capacitors in the compensation network.

Please tell me what equations I need to use to select the values of these components.

I have not been able to find an application note describing how to do this.

  • 0
    TI__Genius 17240 points

    Hi Geoffrey,

    The compensation design of TPS53317 is the same as TPS51317. Please refer to page 20 of TPS51317's datasheet for the calculation of Rc and Cc.

    Attached please find the design tool for TPS53317.

    0550.TPS53317 calculation tool_04.28.11.xls

    Regards,

    Na

  • 0 in reply to Na Kong
    Prodigy 30 points

    For the calculation of Rc and Cc on page 11 of the data sheet we have equation 12:

    Rc = (f0 * Rs * 2pi * Cout) / Gm

    It is not clear to me how we arrived at the value of Rs which according to equation 11 is equal to:

    Rs = Rds(on) * Gmc * Rload

    Since I don't know the values of Rds(on) or Gmc or Rload.

    There is a picture on page 11 of the data sheet which shows Gmc = 1mS and Rload = 8kOhms.

    Are these the correct values of these variables? What is the value of Rds(on)?

  • 0 in reply to geoffrey wall
    TI__Genius 17240 points

    Hi Geoffrey,

    You are right that Rs = Rds,on x Gmc x Rload.

    Rs is the internal current sense gain, which is ACSINT in the electrical characteristics table. ACSINT is trimmed as 53 mV/A typ. Sorry for the confusion.

    Regards,

    Na