https://devzone.nordicsemi.com/f/nordic-q-a/4200/changing-the-nrf51822-s-supply-voltage-at-runtimeWe have an application in which it would be nice to change the supply voltage for our Nordic module (nRF51822 running the Soft Device) depending on which other modules on our board are powered up and in use. This is because the other modules have higheren-USTelligent Community 13Mon, 27 Oct 2014 14:32:16 GMThttps://devzone.nordicsemi.com/thread/15008?ContentTypeID=1Mon, 27 Oct 2014 14:32:16 GMT137ad170-7792-4731-bb38-c0d22fbe4515:c7be50ee-f485-436d-96e7-dea18f1932d1H&#229;kon Alseth<p>Hi Eliot,</p> <p>Dropping the voltage from 3.0 -&gt; 1.8V will not be a preferred solution for your issue. This drop in voltage is to be considered as a voltage ripple, which we do not have a hard specification for, but we recommend that the ripple on VDD is within 100 mVpp.</p> <p>A more preferred solution is to use a level shifter (discrete via two transistors on RXD/TXD or a IC solution).</p> <p>Regarding the GPIO state; when you&#39;re powering up, the nRF is in a RESET-state (which is a undefined state), where the GPIOs are undefined. When the chip has successfully powered up, the GPIOs are disconnected (internally) by default (hi Z).</p> <p>Cheers, Håkon</p><div style="clear:both;"></div>