Clarification on nRF54 Reference Layout Requirements

[Moshe]

Hi,

We’re currently integrating the nRF54 series into a product we’re developing, and we’re using the reference schematic and layout as our guide.

While working through this, a few questions came up that we’d appreciate some clarification on, mainly around how strict we need to be with layout and component choices.

1. In the reference design, many of the passives are 0201.
   For our application, board space is not a constraint, and using 0402 or even 0603 parts would significantly simplify assembly and reduce manufacturing risk.
   If we keep the same topology and relative placement (i.e., same connections, similar trace lengths, no major rerouting or reshaping), but slightly rearrange components to accommodate the larger footprints, is that likely to cause issues?
   How sensitive is the design to the exact physical placement of these passives?
2. The reference layout uses a 4-layer board. Is this effectively a requirement for proper RF and power integrity performance, or is it mainly recommended for robustness?
3. The documentation stresses following the reference layout very strictly, especially around RF.
   If we use a certified SMD Bluetooth antenna instead of a PCB trace antenna, does that relax any of the layout sensitivity around the RF section? Or are the same strict placement and grounding considerations still required around the matching network and feed?

4. For context, we do not need long-range performance. Bluetooth is only used for the initial setup of the device, and the user will be physically close to it during that time.

   Given that, how severe are the consequences if we deviate slightly from the reference layout? Are we talking about a measurable reduction in range (e.g., 30 m → 15 m), or is there a real risk that performance could degrade to the point where Bluetooth would struggle to work reliably even within ~10 feet?

[Szabolcs]

Hi Moshe,

Generally, the problem is not with Bluetooth not working. Yes, the range will degrade, but for 1-3 meters, even the worst antenna will get the job done. However, if you plan to sell a product that has Bluetooth functionality, you'll have to certify that with the authorities (e.g. FCC), and an improper layout will probably cause issues with unwanted emissions. So with that in mind, here are the answers:

1. For the power supply filtering part, this can be OK, but for the matching network, it is highly recommended to use the exact layout with the exact same components, as it is a very sensitive part of the circuit, and modifying it can result in increased harmonic emissions.
2. It might be able to work with a 2-layer design, but we cannot guarantee it.
3. No, the matching network for the chip does not depend on the antenna, as sometimes the unwanted harmonics are not even radiated by the antenna but by the layout and components themselves.
4. You can lower the output power of the chip, this will also decrease the level of unwanted emissions.