LTC4020 Vout issues

[EJustaskaquestion]

Hi,

I have created a PCB board similar to the demo DC42044A

The input is a regulated 30V from a power supply and the output is set to be 11.1V 3.3A.

The issue is that when turned on the power supply is current limited and will only allow ~6.6V @ 0.5A to pass through and the VOUT output of the board is capped at ~7.9V

I've tried to troubleshoot this myself by changing the feedback resistors but have had no luck thus far.

My expertise is not in power electronics so apologies in advance for any obvious misses.

Schematics, Board Layout snips, Gerber Files and Oscilloscope readings are all in the ZIP file below.

 

[cupoftea]

Have you tired setting it up as in LTspice?...and run it there...you will likely then see the problem.
The attached is your schem....you provide layout in CAMtastic, for which we need Altium free viewer to view?

Here is LTC4020 datasheet

https://www.analog.com/media/en/technical-documentation/data-sheets/4020fd.pdf

Your RT=100K, so your Fsw=250khz
(im getting there...will come back soon and further assess your problem)

 

[Easy peasy]

do you have a clear picture of the pcb please ?

 

[KlausST]

Hi,

So if your power supply is current limited somehow you need to
* use an appropriate slow soft start at the LTC4020
* or (temporarily) increase the current limit of the power supply
to ensure the 30V can stabilize.

Klaus