nrf54l15 Cannot use SWD interface

RE: nrf54l15 Cannot use SWD interface

Yeonjun Lee — Mon, 27 Apr 2026 10:55:13 GMT

Oh it was not applied on pcba. I did it after i got a board. And board works fine with 2.2uF Thanks!

RE: nrf54l15 Cannot use SWD interface

Szabolcs — Mon, 27 Apr 2026 10:53:28 GMT

Hi,

what you are seeing here is probably L3 and C21 resonating (forming an LC tank circuit). On your schematic, you are missing a 2.2 uF capacitor on the DECA/DECRF net, that could probably explain the problem.

On the PCB, a VDD trace is overlapping with the GND plane, where you made the rework. Did you cut this trace? (edit: I see that the actual PCB is different, as the capacitor is rotated.)

Did you verify there is no short circuit, and all supply voltage levels are correct? 1V sounds a bit low, the internal voltage should be around 1.2V. What I see on the scope, is that the regulator fails to start correctly and tries again periodically.

RE: nrf54l15 Cannot use SWD interface

Yeonjun Lee — Mon, 27 Apr 2026 08:44:28 GMT

UPDATE:

Found weird volatge peaking on DECA.

Trying to feature out the root cause. Maybe due to putting C21 on bottom size connected with via...?

Peaking rate is approximately 51Khz

UPDATE: Tried to cut the line that connects DECA and DECRF. DECRF was fine. DECA still makes some speak graphs

UPDATE: removed C21. and.. it worked... why......?

RE: nrf54l15 Cannot use SWD interface

Yeonjun Lee — Mon, 27 Apr 2026 00:38:05 GMT

UPDATE: I see the voltage around 1v on decoupling pins. looks fine. And i tried without oled attached. It did not work