RE: NRF54L15 reference design onboarding questions

Kazi Afroza Sultana — Wed, 08 Apr 2026 09:43:36 GMT

(1 kΩ + 3.9 pF) is recommended and you should not leave the pin unconnected (floating).

RE: NRF54L15 reference design onboarding questions

astomi — Wed, 01 Apr 2026 12:31:15 GMT

"The RC filter (1 kΩ + 3.9 pF) on the NRESET pin is specifically chosen due to coupling of the 2nd harmonic from the neighboring ANT"
What is the exact frequency of the second harmonic you are referring to? How it correlates with RC(1 kΩ + 3.9 pF) cutoff frequency of 40MHz?

What would be better: A/ leave 'Reset' pin unconnected or B/ Bypassed by small cap?

RE: NRF54L15 reference design onboarding questions

Kazi Afroza Sultana — Tue, 31 Mar 2026 12:28:32 GMT

Hello,

''1. C13 (reset pin bypass) is 3.9pF. This value is less than parasitic pin capacitance - should it be 3.9nF?''

This is tested and verified. The RC filter (1 kΩ + 3.9 pF) on the NRESET pin is specifically chosen due to coupling of the 2nd harmonic from the neighboring ANT pin to the RESET pin ((+) nRF54Lxx - reset circuitry - Nordic Q&A - Nordic DevZone - Nordic DevZone).

2. C11 (last cap in antenna matching network) is 0.3pF. A u.FL connector pin geometric tolerances or a speck of dust would introduce same order of magnitude error''

I believe you meant. This is for the best RF performance; getting the utmost output power while keeping the harmonics below regulatory limits.

''3. The reference design is 4 layers. I have seen mentions of previous 8 or 6 layer designs. Is 4 layer a latest recommendation''

The latest recommendation is 4 layer PCB design.

5.Given that C9 is referenced to the bottom ground and copper windows under RF circuitry, bottom layer is a primary RF ground. So why RF ground has tracks but not Layer 2 for example?

If we look at the schematic, you can see C6 is grounded through VSS_PA; not directly to the ground plane for creating additional filtering of harmonic components.

To give you accurate answers for rest of the questions, I will talk to team. In the meantime you can send your hardware design to us if you have any.

Thanks.

BR
Kazi

P:S: This is easter vacation time in Norway. So, it may take a bit longer time than usual. Sorry for this incovenience.