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Hi E2E forum!
We've used LM5002 in SEPIC configuration as per example below:
We have just changed the Feedback resistors to have 15V as output.
Our specification is Vin=14V to 20V, Vout=15V at 50mA
From the operation side the SEPIC is working quite good: sweeping from 14V to 20 the output is always stable at 15V. However something strange on the output is happening, it seems ripple but in fact seems to be more a switching noise issue.
At the beginning we was using as switching Diode (D2) a Vishay V8PAL45 but seems to have a high junction capacitance(1400pF) so we changed with a SS16 (less than 100pF).
Changing diode and output capacitor (from electrolitic to ceramic) have improved the ripple as below image to 200mV.
Before:
After:
Zoom on the peak-pulse:
All the test has been performed with a 50mA load.
We're basically looking for suggestion on hot to improve the AC-Ripple/Switching noise at the output: We tried to add a RC snubber in parallel to D2 but unfortunately this have not helped.
Anyone has got similar issues?
Thanks in advance
Davide
Hi Jasper,
Yes exactly the waveform has been measured directly on the output capacitor.
Adding a 0603 100nF capacitor (we have finished 0402) have reduced about 5/7% the spikes.
We'll try add a smaller LC filter, and i'll let you know.
Thanks in advance for your support
Davide