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LT3959 & LT4359: Simulation and Config.


I am tring to design and Ideal Diode & SEPIC converter power circuit for a design I am working on using the above components with similar components and configurations listed in their respective datasheets.

I have been simulating the design in LTSpice and been getting a large ripple voltage on the ouput of the LT3959, my voltage inout range is 4.5V - 24V and my output is 5V Nom. with acceptable range of 4.75V - 5.25V. The ripple I am observing is ~2V Peak to Peak initial transient, and ~1V peak to peak at steady state.

I have tried to correctly select / adjust the capacitor/resistor values of the RC network connected to the Vc pin but I can't seem to lower the ripple much more than this. I notice that the LT3959 LTSpice model is missing the SYNC pin, is this perhaps the reason I am getting these results or is there something else that may be inccorect in my circuit?

I have attahced my LTSpice model, I can't seem to attach the simulation data, but will try again if someone requests it.

Any help is greatly appreciated, thank you.