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I am using a MGDSK10H5,5 in my design for generating 5.5 V. The MGDSK10H5,5 is an isolated DC-DC converter, but I am using it as a non-isolated DC-DC converter; I have shorted input and output grounds of this DC-DC converter.

When I measure the output it's showing 6.21 V instead 5.5 V.

I am using FBMJ2125HM330-T ferrite bead at the output between two 22μF capacitors.

I have attached the circuit diagram I am using currently.

Can someone tell me why I am getting 6.21 V instead of 5.5 V? Is something wrong with my circuit?

enter image description here

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    \$\begingroup\$ A minimum load is required (Minimum 10% load is recommended, operation with no load during more than 1s may partially damage the converter output. ). However, what I see in specs is that a capacitor may (must ?) be wired in place of your short, but a "short wire" is not specified ... \$\endgroup\$
    – Antonio51
    Nov 30 '21 at 14:41
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    \$\begingroup\$ Might be because you've got a very bent and wobbly inductor coil... :-) \$\endgroup\$
    – TonyM
    Nov 30 '21 at 14:53
  • \$\begingroup\$ @Antonio51 I am using it as a non-isolated DC-DC converter; I have shorted the input and output grounds of this DC-DC converter. \$\endgroup\$ Nov 30 '21 at 15:00
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    \$\begingroup\$ @TonyM I tried my best :-) \$\endgroup\$ Nov 30 '21 at 15:00
  • \$\begingroup\$ "Short wire" not specified, ok ... but not prohibited, so you can try, i think it is ok. But the Minimum load is specified, be careful. \$\endgroup\$
    – Antonio51
    Nov 30 '21 at 15:03
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If you're measuring the output voltage with no load, don't do that. The datasheet for this regulator says that the load regulation spec is ±2.5% when the load is between 25% and 100% of rated (450mA - 1.8A), and -2.5% to +20% when the load is less than 25%. 5.5V + 20% = 6.6V, so you're well inside that.

It also says "Minimum 10% load is recommended, operation with no load during more than 1s may partially damage the converter output." so it's really not designed for no-load safety.

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  • \$\begingroup\$ I did power on my 1st assembled board without load. They should have mentioned that clause in a bold and bigger size. \$\endgroup\$ Nov 30 '21 at 14:59
  • \$\begingroup\$ @MightyBeard007 It's like in "contracts" with "insurers"...Always read the clauses in very small letters ... :-( Sometimes, I fail ... :-) \$\endgroup\$
    – Antonio51
    Nov 30 '21 at 15:11
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    \$\begingroup\$ It's a hard way to learn about it, but minimum load requirements are common for regulators of this type. \$\endgroup\$ Nov 30 '21 at 15:17
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    \$\begingroup\$ @Antonio51 I will keep it in mind \$\endgroup\$ Nov 30 '21 at 15:18
  • \$\begingroup\$ @ChrisKnudsen I have used coupled DC_DC converters, but this is the first one I am seeing about minimum load requirements. \$\endgroup\$ Nov 30 '21 at 15:20

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