Issue with Capacitor C5 Value in the 54L15 (QFAA QFN-48) Reference Circuit.

[zhanxy]

In version 0.8 of the reference datasheet for the 54L15 (QFAA QFN-48), the capacitance value for C5 is specified as 10nF. Why was it updated to 2.2nF in version 0.9? What is the reason for this update, and what are the risks if 10nF is still used?

[Szabolcs]

Hi,

the reference circuitry for the nRF54L15 is still under development. In order to optimize RF performance, harmonic emissions need to be minimized. RF can leak through the PA's power supply pin (DECRF), and can lead to unwanted emissions, which are suppressed by the capacitors on these pins. These capacitors have to be carefully selected to high frequency, and it was found that 2.2nF is the optimal value for suppressing RF emissions.

If you are not using the recommended components, you can experience higher harmonic emission levels which might lead to failing compliance tests.