https://devzone.nordicsemi.com/f/nordic-q-a/10397/nrf51822-adc-accuracy-without-an-external-crytsalThe Product Specification makes it clear that the given levels of accuracy for ADC measurements are only possible when using an external crystal for the HFCLK. We have one of those on our current prototype boards are are now looking to remove it. Theen-USTelligent Community 13Tue, 24 Nov 2015 08:41:11 GMThttps://devzone.nordicsemi.com/thread/38605?ContentTypeID=1Tue, 24 Nov 2015 08:41:11 GMT137ad170-7792-4731-bb38-c0d22fbe4515:1fe817ff-013c-4234-b605-87d1ec7ef55dOle Bauck<p>The &quot;Block resource requirements&quot; in chapter 8.3 says &quot;requires HFCLK XOSC&quot;. The problem here is that the comment is also with the ADC even though this can be run on the RC oscillator with a lower accuracy.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/38604?ContentTypeID=1Mon, 23 Nov 2015 21:17:11 GMT137ad170-7792-4731-bb38-c0d22fbe4515:2720e3de-89d8-486a-890c-a9192d51852eEliot Stock<p>I had no idea, thanks. Don&#39;t think the PS makes that very clear.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/38603?ContentTypeID=1Mon, 23 Nov 2015 13:49:26 GMT137ad170-7792-4731-bb38-c0d22fbe4515:2e456499-3973-43a9-954e-e33cfafd5e71Ole Bauck<p>If you are doing BLE you cannot remove the HFCLK crystal, this is mandatory for the radio to work.</p><div style="clear:both;"></div>