Reducing SW node ringing - LT3958 SEPIC converter

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gautam023

Joined Apr 26, 2021
11
Hello everyone,

I am trying to design a power supply for Arduino and other sensors from a 68V battery pack. The voltage outputs I require are +15,+5,-15. I am using an LT3958 for this reason. I have followed the design procedure according to the datasheet (linked here). When I do the analysis in LTSPICE I am getting a huge SW node ringing. It is 10V above supply. I have tried changing input and output capacitors without seeing much difference. I have attached my design files below.
For all those who can help thank you in advance.
 

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Ian0

Joined Aug 7, 2020
2,252
How well does it work in real life?
Have you tried it with coupled inductors?
Have you put appropriate amounts of series resistance for the inductors and ESR for the capacitors in the simulation?
Why use a SEPIC? If you only ever have to step down, wouldn't a buck be easier?
If you don't need much current from the -15V you can generate it with an extra winding on the inductor.
 
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