https://devzone.nordicsemi.com/f/nordic-q-a/121811/nrf54lxx---reset-circuitryDear all, I am wondering, what is the reason for C13 being 3.9pF for QFN package, while there is no capacitor on WLCSP reference design? Could we use like 10nF instead? From what I see, this is a part of low-pass filter for RESET line from externalen-USTelligent Community 13Fri, 30 May 2025 06:42:56 GMThttps://devzone.nordicsemi.com/thread/537480?ContentTypeID=1Fri, 30 May 2025 06:42:56 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6518c500-054a-4126-af23-1966ead27c61mathiaso<p>You&#39;re very welcome, Simon!</p> <p>Closing the ticket.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/537274?ContentTypeID=1Wed, 28 May 2025 04:48:55 GMT137ad170-7792-4731-bb38-c0d22fbe4515:90f44ce4-f840-466f-bc07-634795beca18simonk<p>Thank you Mathias, that clarifies everything!</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/537180?ContentTypeID=1Tue, 27 May 2025 12:45:51 GMT137ad170-7792-4731-bb38-c0d22fbe4515:b5c48803-1689-464f-9715-5cf492be1800mathiaso<p>Hi, Simon.</p> <p><a href="https://devzone.nordicsemi.com/members/turboj">Turbo J</a> is partly onto the reason for this.&nbsp;The 3.9 pF shunt cap is there to prevent spurious 2nd harmonic emissions in TX from the RESET line.</p> [quote user=""]while there is no capacitor on WLCSP reference design?[/quote] <p>This is because there are longer internal bonding wires in the QFN package.</p> [quote user=""]Could we use like 10nF instead?[/quote] <p>No.</p> <p>Best regards,<br />Mathias</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/537071?ContentTypeID=1Tue, 27 May 2025 07:53:35 GMT137ad170-7792-4731-bb38-c0d22fbe4515:fab6a2cf-7488-4632-bbd8-7b977b4d2592Turbo J<p>Look at the pin numbers. Reset is right next to the antenna. </p> <p>That means you must be very careful, that cap is likely black HF magic in order to prevent ANT influencing the Reset signal. Larger MLCC may not be effective at 2.4 GHz.</p> <p>The WLCP reference may have different magic in the <em>layout</em> which may be relevant here.</p><div style="clear:both;"></div>