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I am designing a PCB that needs to convert 24V DC to 5V DC @ 8 amps. I would like to use an off-the-shelf converter and virtually everything in that range is an isolated DC-DC converter. Is there any harm in connecting the VOut- to the VIn- and destroying the "isolated" part of the converter (that I do not need in the first place)? I am planning on using a Murata UEI-30W.

I just want to make sure that there is no downside (i.e. power supply blowing up or unstable) if I connect the input and output grounds. The reason the grounds cannot be isolated is that the devices that requires 5V will share a common metal chassis ground with the devices that require 24V. So, there will be no isolation of grounds regardless.

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  • \$\begingroup\$ Should I isolate grounds of an isolated DC/DC converter? electronics.stackexchange.com/questions/35800/… \$\endgroup\$ – Abdella Jul 21 '15 at 23:03
  • \$\begingroup\$ The only downside is that you may be paying more for the isolation (in <currency units> or perhaps in efficiency or some other criteria). \$\endgroup\$ – Spehro Pefhany Jul 21 '15 at 23:32
  • \$\begingroup\$ Thanks - I saw that other question but it was "when should I isolate." In my case I know I don't want to, but I wanted to make sure it was OK to use an isolated PS but not isolate. \$\endgroup\$ – bode Jul 22 '15 at 17:01
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An isolated DC/DC converter allows the input and output grounds to be isolated, but does not require them to be isolated.

If the input and output grounds must be isolated, Murata should state that very clearly on the datasheet, but I can't visualize any reason for such a requirement.

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