I have a simple LT3663 circuit that I'm using to regulate 15v down to 13.8v.
("24v" is actually 15v in, and "15v" is 13.8v out.) This works almost perfectly. It current limits properly, etc. However, for some reason, the LT3663 only outputs 10.4v, at any current draw below the limit. It regulates perfectly at this voltage. Messing around with R18 and R20 values didn't change anything at all.
It's...a bit ugly. However, I think it's pretty close to the reference in terms of placement and grounding and routing.
Why is this?
Something very odd is happening, indeed. I just pulled R18 off the board completely (grounding FB), and the vreg still maintains 10.2v.