https://devzone.nordicsemi.com/f/nordic-q-a/12195/supply-voltage-issuseHi everybody. I am making a custom circuit which using external LDO with output is 2.5 volt. Then I use this 2.5 volt as VCC_nrf for the nrf51 chip which using internal LDO mode. Is there any problem with this condition ? Thank you very muchen-USTelligent Community 13Mon, 29 Feb 2016 08:37:54 GMThttps://devzone.nordicsemi.com/thread/46152?ContentTypeID=1Mon, 29 Feb 2016 08:37:54 GMT137ad170-7792-4731-bb38-c0d22fbe4515:e87e868e-652a-437f-9e97-b588a6e8b30b&#216;yvind Karlsen<p>Hi,</p> <p>The supply voltage for internal LDO mode ranges from 1.8 V to 3.6V, this means that you should be fine with 2.5 V. For more information see chapter 7 of the <a href="http://infocenter.nordicsemi.com/pdf/nRF51822_PS_v3.1.pdf">product specification</a>.</p> <p>Be aware that if your external LDO provides an unclean output you might have problems with the radio not working as intended, the ripple should be below 100 mV. If the ripple has a frequency of 1MHz, 16MHz etc. it will be modulated directly into the radio and the tolerance will be much less than 100 mV ripple for those cases.</p> <p>Best regards,</p> <p>Øyvind</p><div style="clear:both;"></div>