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Background : In one of my board i have used LT8471 as DCDC , as my cards being analog cards, i tried maximum to seperate the power network and analog chain from noise, my initial problems with dc-dc noise are answered here at Apporach1 and Approach2 after which i have curbed the noise to <100mV by incorporating CLC pi filters at dcdc output

Problem : still i see some spurious switching noise pulses appearing in my analog channel , in order to completely eliminate switching noise , i wish to do noise analysis like we do with case of opamps, similary i want to measure the switching noise on LTSpice and then apply correct combination of pi filters to eliminate them

below is the the schematic of IC i am using, i have just added a CLC pi filter at the output where L is a 10uH and C being combination of 1nF,100nF,47uF

enter image description here

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  • \$\begingroup\$ Just look at the spectrum of the output voltage? \$\endgroup\$ – PlasmaHH Aug 10 '18 at 12:46
  • \$\begingroup\$ @PlasmaHH , usual simulation wont show a switching noise, it just shows the ramp up of voltage and it attaining a stable voltage output, but not switching noise \$\endgroup\$ – kakeh Aug 10 '18 at 12:48
  • \$\begingroup\$ How low is the ESR of those 47uF? Should be <0.01 Ohm at least. Curious, did you consider using a LDO linear reg after the switcher? For sensitive analog circuitry, that will likely work better than any amount of filtering. \$\endgroup\$ – rdtsc Aug 10 '18 at 12:54
  • \$\begingroup\$ @kakeh: have you actually simulated the schematic you are showing? \$\endgroup\$ – PlasmaHH Aug 10 '18 at 13:06

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