[SOLVED] MT3608 boost circuit issues.

[gmc]

I've trying to get a project working where I need to provide 12V from 5V (USB)

I am using the MT3608 and have seen a bunch of circuits where this is possible. Not for me though

https://www.olimex.com/Products/Breadboarding/BB-PWR-3608/resources/MT3608.pdf

Circuit I have is attached.


The issue I have is if I provide 5.2V from my PSU it works as expected. Get a nice stable 12V out.

If however I power from USB, or drop the voltage to 5.1V the output drops to 5V. 

Pulling my hair out. Swapped out the MT3608, same issue.

Does anyone have any experience with these chips and has had similar issues?

[gmc]

Solved.

The 22uF input cap was dead - open circuit. Replaced and now its working even down to 4V.  Very odd, didn't think the input cap would make much difference but obviously it does.