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TPS7H3301-SP: Gm Table - Excel Calculator

Ryan.Bishop
Expert 3900 points
Part Number: TPS7H3301-SP

Hello,

I am trying to properly use the excel calculator that is provided for this part, but I am running into a few uncertainties. 

  1. The tab containing the Gm lookup table only contains data for DDR1. This is a DDR3 application. I noticed with all the cells populated, if you simply change between DDR1-4, the Gm recommendation does not change...

  2. What's the method for selecting the appropriate crossover frequency?

  3. Is the ESR that gets calculated in the bottom a minimum or maximum value we should have? Or is it simply a target?

Thank you!

Regards,
Ryan B.

  • 0
    TI__Genius 17035 points
    Hello Ryan,

    The applications engineer for this part is in Dallas and is already gone for the weekend. He might not be able to reply until Monday.
  • 0 in reply to Kirby Kruckmeyer96848
    TI__Expert 3900 points
    Hi Kirby,

    Thanks for letting me know. I figured that would be the case, but I wanted to get this posted now so I don't forget come Monday. Have a nice weekend,

    -RB
  • 0 in reply to Ryan.Bishop
    TI__Mastermind 22475 points
    Hey Ryan,

    It looks like the GM values were specifically measured for DDR4 in the excel calculator.
    However, since the logic of the device is from a separate supply, the gm of the device shouldn't be effected by which DDR is being used.

    There is less of a method for determining crossover frequency, and more that the crossover frequency will be dependent on the output capacitance in a design. My best suggestion is choose a crossover frequency based on the output capacitance you plan on for the design, I understand the calculator does it the other way around.

    The ESR calculated is the maximum value that can be used without causing issues with gain margin for current values.
    This is the total ESR, thus remember if two 6 mOhm capacitors are used, they will have an ESR of 3 mOhm.
    Details for what to do if this value is too low are detailed in the datasheet.

    Thanks,
    Daniel