https://devzone.nordicsemi.com/f/nordic-q-a/17490/running-nrf51822-with-1-1v-batteryHi I came across this article: www.nordicsemi.com/.../Bluetooth-Smart-hearing-aid-receives-stereo-audio-direct-from-iOS-devices-and-can-recognize-and-optimize-settings-in-frequently-visited-places They are using nrf51822 WLCSP with a battery sizeen-USTelligent Community 13Thu, 03 Nov 2016 10:20:02 GMThttps://devzone.nordicsemi.com/thread/67229?ContentTypeID=1Thu, 03 Nov 2016 10:20:02 GMT137ad170-7792-4731-bb38-c0d22fbe4515:14d15c8d-017f-41c3-bdaf-15f20655391cJ&#248;rgen Holmefjord<p>Hi,</p> <p>If you want to use a battery with a voltage outside the specified supply voltage range of 1.8 V to 3.6 V, you will have to add a DC-to-DC converter to your design. A boost (or step-up) converter can be used to increase the supply voltage.</p> <p>Best regards,</p> <p>Jørgen</p><div style="clear:both;"></div>