I have a PCB with nRF52833 and nPM1304, I assembled 3 identical PCBs, 2 of them work 1 does not
I am using 2 available Buck coveters, first outputs 1.8V for powering IC on my PCB, second is used to power the LEDs. (Schematic for nPM1304 attached, it very much copies the reference schematic)
So after assembling one of the PCB I observed weird behavior of 1.8V line when it was going to 300mV every 1.3 seconds
.
After long session of debuging I found out that if remove capacitor of VOUT2, it starts to work normaly and output constant 1.8V (however VOUT2 becomes very nosy, but that expected, I also tried to replace capacitor on VOUT2, with 4.7uF capacitor rated for 15V, issue came back).
But it only stable if I power is from VBAT, if I will use USB input voltage just jumps from 1.8 to almost 0V every 113ms
My issue is that that happens only on one out of 3 assembled PCBs, so what could be the issue?
P.S. I was able to to program nRF52833 via SWD connector and directly supplying 1.8V power line if that important
