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TPS5401 Data Sheet Error?

M. Simon
Prodigy 30 points

Other Parts Discussed in Thread: TPS5401, LM22674

I'm doing a spread sheet design of a TPS5401 Buck Converter. The design information from your data sheet does not even get me close to the Cp and Cc (compensation) capacitor values you show on the Workbench for that part. The resistor value Rc is close (less than 10% difference). 

I used the same values for the pertinent parts that you use in the workbench, Inductor, output capacitor, maximum current etc. 

I'm going to look at some other similar buck converter data sheets to see if I can figure out the error.

  • 0
    TI__Intellectual 890 points

    Hi,

    The equations are slightly different between the two tools. Here are some equations that we use for selection in WEBENCH for this device.

    Rcomp = vout / (vref *gmea * gainXover);

    Ccomp = 1/ (2* PI* Rcomp* fpmod);

    Ccomp2 = Max (1/( PI* Rcomp* fsw), cout*cout_esr /Rcomp )  ;

    where,

    - gainXover: Gain of the power stage at crossover frequency (This gain takes into consideration the slope compensation of the IC. This might be slightly different from the excel calculator)

    - fpmod is the dominant pole.

    - note: Ccomp2 is placed using the min of csw/2 and ESR zero.

    In addition, the output cap derating could be different between the two tools.

    Thanks,

    --Abhishek

  • 0 in reply to Abhishek Gupta - WEBENCH Design Center
    Prodigy 30 points

    I went with the LM22674 in the interim. So you won't lose the business.