https://devzone.nordicsemi.com/f/nordic-q-a/16620/separate-ain-to-check-battery-level-is-okUsing nRF51822. I use external DCDC to supply concurrent 3.1V for VDD(PIN1). Then I have no way to check bettery level. So I connect battery and AIN4(p0.03) separately, directly. Does this circuit can make side effect, as if radio performanceen-USTelligent Community 13Fri, 30 Sep 2016 12:33:36 GMThttps://devzone.nordicsemi.com/thread/63565?ContentTypeID=1Fri, 30 Sep 2016 12:33:36 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d576c30c-2ebd-4746-9caf-3963cfeeb53fJake<p>Sorry for late reply.</p> <p>As you mentioned I checked ripple on the VDD pins. And I found too much of ripple in VDD, DCDC generated.</p> <p>I asked this to provider of DCDC converter, and they suggested correct value of capacitor of VDD and Feedback line.</p> <p>Now it it works.</p> <p>Thank you Einar Thorsrud.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/63564?ContentTypeID=1Fri, 23 Sep 2016 11:13:30 GMT137ad170-7792-4731-bb38-c0d22fbe4515:90533605-5383-4993-87a2-4fe6af2cdbbaEinar Thorsrud<p>I don&#39;t really understand why you get bad radio performance when measuring with the ADC. Are you confident that that is the case? As you are using an external DC/DC there will be some ripple on the supply voltage. Can you measure how much ripple you have on the VDD pins?</p> <p>How have you configured the ADC in your case? Without any external components you should configure it with 1.2 V VBG reference and 1/3 prescaling. Also, have you seen the <a href="https://devzone.nordicsemi.com/blogs/30">Measuring Lithium battery voltage with nRF51</a>? In order to get precise measurements, you should use an external voltage divider and capacitor, as described in the blog post. Note that none of this explains bad radio performance, though.</p><div style="clear:both;"></div>