LT8362 Troubleshooting

Hi,

>> I have built the circuit to boost 5V input to *ultra low noise* 48V
If you need that, it would require other / more complex circuit.

If your R4 is indeed 1 mOhm then it is clear that the LT8362 is not switching as it tries to regulate to Ufbx = 1,6V. But output will be at least V_in - diode drop.

The output circuit is really strange to me. It will lower your output voltage at about 0,6V, has bad HF supression, no regulation and no overcurrent protection.
You would be better off to use a ferrite bead and a ceramic cap to filter HF out of output.
The problem with step-up converters is that their current pulse to the output easily mess up ground potential as this produce symmetric noise on the rails and ground.

If you would use an LDO you get good regulation and good accuracy of output voltage.
Also an sepic converter should be more quiet, because the current that recharges output capacitor is triangle shaped.

Why do I need more complex circuit? The article above is written about Analog Devices' chip by Analog Devices' staff, it claims this circuit has great properties.

As for the values — I have literally copied the values (including R4) from the schematics in the article above:


With the changes to a few components that are described in the end of the article, to take 5V input.

Is the article wrong? Should I not trust the data AD writes about its devices? I think I am most likely missing something of key importance, but it shouldn't be the R4 value...