I have read through the other posts regarding the LTC3350 and am having a similar issue to others.
The system is 24V in 24v out.
The Chip powers up and appears to be functioning as intended apart from the 4 x 40F (3V) supercaps not charging.
PFI is above the threshold (1.17V) at 2.04V however upon reading the PFO pin it is low indicating that this does not appear to be true. (Screenshot 1 of PFI on startup vs Screenshot 2 of serial output of PFI pin.)
RPF1 was changed from 820K R to 499K R reducing the threshold voltage from 21.6V to 13.6 V in an attempt to solve the PFI issue, to no avail.
Switching and 2.5V line appear stable.
Registers appear normal.
Any help is appreciated, please see attached screenshots.
PFI pin on startup
Serial output of PINs + external current sense IC reading.
Registers
SW pin
Input Pin
VCC2P5
Schematic
(RPF1 is now 499K not 820K)
Layout bottom
Layout top