https://devzone.nordicsemi.com/f/nordic-q-a/72784/purpose-of-32khz-crystalOur device has been in use for a year using the nRF52840. We elected to not load the 32KHz crystal on our board. Everything seems to work OK and we have no BTLE issues, however I still wonder if we should have fitted the 32KHz crystal. I have searcheden-USTelligent Community 13Mon, 15 Mar 2021 08:52:58 GMThttps://devzone.nordicsemi.com/thread/299685?ContentTypeID=1Mon, 15 Mar 2021 08:52:58 GMT137ad170-7792-4731-bb38-c0d22fbe4515:42ba5d40-844b-43e2-9e08-ddd72fa61066Kaja<p>Hi Leon,<br /><br />using an external 32.768 KHz crystal is optional:<br /><img src="https://devzone.nordicsemi.com/resized-image/__size/320x240/__key/communityserver-discussions-components-files/4/pastedimage1615794529088v1.png" alt=" " /><br /><br /></p> <p></p> <p>You can also achieve lower current consumption, by using an external crystal.&nbsp;</p> [quote user=""]I see many answers refer to the 2.4G radio but why would a 32KHz crystal be used here?[/quote] <p>&nbsp;Probably mixing with the 32 MHz crystal.&nbsp;<br /><br />Best regards,<br />Kaja</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/299679?ContentTypeID=1Mon, 15 Mar 2021 08:33:28 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5fcfb7c9-f855-4f04-8779-ed707df6eca5Dmitry<p>Hi Leon,</p> <p>32k crystal helps to save battery power in two ways:</p> <p>- crystal ocsillator draws ~0,23uA, RC oscillator ~0,7uA</p> <p>- when device is in connection, CPU should wake up right before the connection event is started, taking into account possible drift caused by oscillator. For example, with +-500ppm RC and 1-second connection interval, CPU should wake up at least 500us earlier, and wait for incoming packet up to 1ms. With 10ppm crystal, this window is about 50 times shorter.</p><div style="clear:both;"></div>