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I’m having difficulties with settings the right values for the comb / compensation for some SMPS circuits I’m working one. Is there a good way to set them right? To make sure of stable operation in the full load range of the SMPS.

Hope some one can give me some tips on what the best way is for this

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  • \$\begingroup\$ How about an example circuit to unbroaden the massive scope of this question? \$\endgroup\$
    – Andy aka
    Commented Sep 10, 2014 at 6:54
  • \$\begingroup\$ i have the issue on the moment with 2 circuits. a SG2525 and another with a LTC3787 !main part schematic the ITH is the compensation part \$\endgroup\$
    – niels1
    Commented Sep 10, 2014 at 8:30

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I assume you mean the resistor and capacitor in series that you'll find on many Linear Technology switcher ICs that compensate the regulation loop.

Usually standard values are given in the datasheet, but Design Note 186 from Linear Technology describes how you can actually test the transient response dynamically which allows you to optimize the component values. It's a compromise between settling time and over/undershoot.

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  • \$\begingroup\$ thanks! i used the standaard values. but it's oscillating, 2 engineers from linear passed by (very good service) but they did not know why my pcb had this issue. as they told me the design is good, layout as well. and all signals also looked ok only the output has about 6V rimple on the 24V because of oscillation. so i hope that i can solve the issue with the feedback loop. as i don't know were else i have to look for this issue \$\endgroup\$
    – niels1
    Commented Sep 10, 2014 at 10:35
  • \$\begingroup\$ What's R39 doing there? \$\endgroup\$
    – jeroen74
    Commented Sep 10, 2014 at 11:31
  • \$\begingroup\$ based on linear application note. you have to interconnect the compensation pins if you use more then 1 controller. this was also comfirmed by the people from linear. to make sure i also tested the master and slave apart but none of it solved my issue \$\endgroup\$
    – niels1
    Commented Sep 10, 2014 at 12:23

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