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TPS61175-Q1: what are limitations of increasing soft start capacitor or changing its dielectric from COG to X7R?

Part Number: TPS61175-Q1

i would like to increase the soft start capacitor in this design to 0.1uf to double the startup time and reduce peak startup current under rated load. present value of Css is 47nf, the only value allowed in the design (attached). questions i have are

1- is 47nf the max value allowed for this design?

2- if a larger value of 0.1uf is allowed, can the cap dielectric be X7R instead of COG/NPO since COG/NPO is not available for larger cap values.

3- apart from reduced peak startup current, what other considerations, concerns are created as a result of doubling teh startup time?

22V 50mA 85C TPS61175QPWPRQ1.pdf

  • Hi Tom,

    Thank you for reaching out.

    1. 47nF is not the max value allowed for SS. A 47-nF capacitor eliminates the output overshoot and reduces the peak inductor current for most applications.

    2. Yes, X7R is OK.

    3. No other obvious concerns exist as I know.

    Let me know if you have other questions.