nRF5340 DK not powering correctly over USB — only works on coin cell (dim/blink behavior).

RE: nRF5340 DK not powering correctly over USB — only works on coin cell (dim/blink behavior).

Peter C — Fri, 23 May 2025 23:15:03 GMT

Just a follow up, I have received the package and everything is working. Thanks again.

RE: nRF5340 DK not powering correctly over USB — only works on coin cell (dim/blink behavior).

Peter C — Sat, 17 May 2025 08:34:58 GMT

Hi William,

Thanks for your help on this. I have emailed you the information.

Regards,

Peter

RE: nRF5340 DK not powering correctly over USB — only works on coin cell (dim/blink behavior).

WSeverino — Fri, 16 May 2025 11:36:48 GMT

Peter - I am the RSM for Texas. Please send me an email at william.severino@nordicsemi.no with your address and I will ship you a new kit.

RE: nRF5340 DK not powering correctly over USB — only works on coin cell (dim/blink behavior).

Peter C — Fri, 16 May 2025 06:11:00 GMT

Following your recommendation, I investigated the board’s power behavior since it never enumerates over USB and cannot reach the point where a debug MCU firmware update is possible. Here's a summary of my findings:

Key observations:

USB power (VBUS) reaches U10 (boost converter) and is correctly boosted to ~5V (V5V).
U11 (buck converter) successfully generates ~3.0 V (VREG) from V5V.
Power from VREG is gated through U13 then U14 (TCK106AG load switchs), which is controlled by the VSUPPLY_EN signal.
VSUPPLY_EN fails to reach a valid logic-high level except briefly (~2.6 V) during startup in “VDD” switch mode. Once the switch is moved to “USB,” or if power is cycled with the switch in USB mode, VSUPPLY_EN drops to 0.4 V or 0 V and does not recover unless the board is fully power-cycled in with SW9 in VDD mode.
The VSUPPLY_EN net is pulled low by Q9, an NMOS transistor whose gate is driven by the drain of Q3, another NMOS or by the switch SW9 its hard to tell if Q3 is overriding the VDD_NRF_SENSE net causing the collapse I am seeing.
Q3’s gate is tied to VSUPPLY_EN which can be grounded out by Q9. It's not readily apparent to me what the Q3/Q9 circuit is supposed to do but it is definitely able to be put in a strange state it cannot recover from unless you power cycle the board. (strange state meaning it goes to 2.6v or 0.4v and decays to 0v never to recover until you power cycle SW8)
When VDD_NRF_SENSE changes state (e.g., when USB mode is selected), Q9 turns ON, pulling Q3’s gate low and turning it OFF — which in theory should allow VSUPPLY_EN to rise.
However, the signal behavior does not align cleanly: VSUPPLY_EN consistently fails to rise above 0.4 V in USB mode, and the board never fully powers up or enumerates.
It appears that the logic between VDD_NRF_SENSE, Q9, and Q3 is preventing U12 from enabling, which leaves VDD and the debug MCU under-powered. (IMCUs VDD ~ 1.6v)

At this point, the board appears to be blocked by internal power control logic that fails to enable the core voltage rail (VDD_IMCU) necessary for USB operation. It does not draw high current, it just locks itself out. I’ve confirmed that all power rails before the switching logic are functional and that none are shorted to ground or any other net.

One other bit of information, since my engineering goal is to talk to more than one chip over bluetooth, I bought a second board. I plugged the new one in today and it powered right up without issue and enumerates on the USB bus on the exact same cables and computer.

Please let me know if you’d like additional signal traces, or whether this board may be eligible for RMA.

Best regards,

Peter

RE: nRF5340 DK not powering correctly over USB — only works on coin cell (dim/blink behavior).

Sigurd Hellesvik — Thu, 15 May 2025 11:34:08 GMT

I ask becaues there are two types of debugger chips on the DKs. You got the new one.

With this one, you can perhaps try this:

"nrfutil device x-update-debug-probe-firmware"

It is a long shot, but worth a try.

Other than that, the symptoms you see can perhaps be due to a short between VDD or 5V and GND. Can you try to measure that?

RE: nRF5340 DK not powering correctly over USB — only works on coin cell (dim/blink behavior).

Peter C — Wed, 14 May 2025 15:33:39 GMT

Hi Sigurd,

My sticker says:
PCA10095

2.0.2

2024.3

1050012970

RE: nRF5340 DK not powering correctly over USB — only works on coin cell (dim/blink behavior).

Sigurd Hellesvik — Wed, 14 May 2025 14:57:37 GMT

Hi,

Which version of the DK do you have? (The info on the sticker)

Regards,
Sigurd Hellesvik

RE: nRF5340 DK not powering correctly over USB — only works on coin cell (dim/blink behavior).

Peter C — Tue, 13 May 2025 22:02:06 GMT

Follow-Up (Power Issue Diagnosis):

Quick update based on voltage measurements:

VDD rail measures only 1.5–1.8V under all power sources (USB, Li-Po, coin cell).
USB 5V input is present, but LED5 never stays on and the board does not enumerate via IMCU USB.
On coin cell (PowerSource = VDD), the board runs normally — 4 user LEDs blink at full brightness. The cell drops briefly to ~2.7–2.8V under load, then recovers to 3.0V when removed, suggesting no excess draw.
USB_VDD line near the nRF5340 USB port reads ~1.8V, possibly due to backfeed while on coin cell?

This points to a likely power regulation or switching fault on the board, preventing proper VDD. Please advise if further steps are recommended or if this warrants replacement.