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Step down 48v input POE to 4 outputs 3.3v/5v/12v/custom
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Stealthrt:
Hey all I have been searching for a already-built solution that would output 3.3vdc, 5vdc and 12vdc @ 5a. I have found that here:



However the issue is that I will be feeding this 48vdc (POE) and it seems that the max this thing can take in is 40v.
Do you think it will be fine with 48v? Is there anything I could add to the board so that it can take up to 50v?

LM2596 datasheet: https://www.ti.com/document-viewer/LM2596/datasheet

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Across post:
https://forum.allaboutcircuits.com/threads/step-down-48v-input-poe-to-4-outputs-3-3v-5v-12v-custom.166040/
https://www.electro-tech-online.com/threads/step-down-48v-input-poe-to-4-outputs-3-3v-5v-12v-custom.158171/
andy3055:
48 volts will be too high for those regulators. Also the caps are 50 volts max. Not sure if any of them are on the input side and if they are, there is not enough safety margin.
Stealthrt:

--- Quote from: andy3055 on January 03, 2020, 06:21:52 pm ---48 volts will be too high for those regulators. Also the caps are 50 volts max. Not sure if any of them are on the input side and if they are, there is not enough safety margin.

--- End quote ---

Could I exchange the LM2596 with LM2576 (http://www.ti.com/lit/ds/symlink/lm2576.pdf)? That ladder seems to be tolerant up to 60v.
Vovk_Z:
There is "HV" version of those dc-dc IC. It has 60V max.
andy3055:
Yes, as Vovk_Z stated, you can do that. But I thought you wanted a ready made thing. If you plan to replace the regulators in what you buy, you need to consider the other stuff also like the caps and anything else there may be. Then the whole idea of "ready made" goes out the window!

In this case, you might as well design your own circuit based on the HV versions of the regulator as in the spec sheet you referenced. Why buy something that you need to modify? Not to mention you will be replacing the most expensive parts on that board. Does not make any sense.
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