Noise on LT8652S and LT8364 outputs

Hi Jaslau,

Thank you for reaching out. Can you also probe the switch node as well? Is it jittering? 

Can you also send me the LTspice model file? Thank you.

Do you have the actual schematic file?

Regards, 

Peter Pham

Thanks for your answer!

Here are the measurements of the switch node:

+15V 1.5A:

-15V 1A:

+5V 1A:

+5V 0.3A:

So yes, the +5V seem to be really off.

Here is the schematic (The LTC4365 circuit is not yet populated for the measurements. It started motorboating in some situations, but I wanted to solve this noise problem first.):

PDF

And here is the LTspice file:

0412.PSU.asc

Ok, I just realized that LTspice is pretty much simulating the result I have on the -15V output (not on the +15V though). Even when using the exact schematic from the app note (site 26) its simulating like this:

Any suggestion for smoothing this a bit more (my aim was to get 0.001% ripple + noise)?

I could reduce the noise on the +15V rail a bit by increasing the capacitor on VC1 to 1nF. Also at my last measurements the oscillation on the +5V rail was gone (maybe after resoldering, I am not really sure).

Please consider putting smoothing LDO's at the output. www.analog.com/.../ldo-linear-regulators.html