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TPS53353: Loop stability

Zoey Wu
Expert 5855 points
Part Number: TPS53353

Hi team,

My customer is using TPS53353 and  their SCH is as attached.

But they found that when testing the tps53353 loop, the test results are poor especially after the 100kHz, do u have any advise on improving the loop stability? 

p3v3(1).pdf

  • 0
    TI__Genius 11495 points

    Hello,

    I am currently looking into this. Please allow me a few days to provide a response.

    Thanks,

    Calan

  • 0
    TI__Mastermind 26830 points

    Zoey,

    Please check the design with the excel calculator tool and then share it here.

    https://www.ti.com/tool/download/SLURAZ7

    Also, share your measurement technique for loop response and any measurements.

    Thanks,

    Amod

  • 0 in reply to Amod Vaze
    TI__Expert 5855 points

    hi  Amod,

    my customer  has deigned according to the excel.

    but when they test the bode plot, the performance is really bad over 100kHz. the tested graph is as below.

  • 0 in reply to Zoey Wu
    TI__Mastermind 26830 points

    Hi Zoey,

    Since there is a RCC injection network, the injection signal for frequency sweep must also pass through that path. It looks likely that is not the case with your schematic since there is only a R1181 shown in the schematic which will not include the other FB path from the RCC injection network. So, you need to add a bypass cap of around 220nF in parallel to the R1181 and also disconnect the direct connection of C6818 to VOUT and instead connect it to the bottom of R1181. This is only required for bode plot measurements and the circuit you have currently should work fine just as is but bode plot measurements may not be easy to do. Please refer to https://www.ti.com/lit/an/sluaaf4a/sluaaf4a.pdf for details on the schematic connections. Also, the 1kohm/100nF (R1180/C6818) needs to be updated to keep the same time constant but not load the signal when adding the bypass cap for bode plot measurements. This can be done by increasing the R1180 to alets say 10kohm and reducing the C6818 to 10nF instead.

    If this is tedious, I would just recommend taking a load transient and confirming there is no ringing during overshoot/undershoot which will also show you a measure of stability.

    Thanks,

    Amod