Power supply

[BradJ]

Hello,

We are designing a wearable that is going to use the nRF52840 and I have a question about supplying power to the unit.  We are planning on using a coin cell to power the unit, and I am wondering whether or not we require a dc-dc converter (buck-boost) to consistently supply 3.3V to the device, or if I should connect the battery directly to the nRF52840.  Also, the ANT interface shows a U.FL connector being used, but can we also use a PCB antenna?  If so what are the guidelines for a PCB antenna?

Thanks!

Brad

[Jared]

Hi,

I suggest that you look at the hardware drawings of the nRF52840 DK that has a coin cell option for power supply. From the description of the power supply on the DK: 

"For the 5 V domain, there are two regulators, one fixed 3 V buck regulator and one voltage follower regulator that follows the VDD_nRF voltage. The coin cell battery and external power supply are not regulated".

 

Also, the ANT interface shows a U.FL connector being used, but can we also use a PCB antenna?  If so what are the guidelines for a PCB antenna?

 The nRF52840 DK use a 1/4 wave PCB antenna. The guidelines you should follow are the requirements that is specified in the datasheet of the antenna. This will ensure maximum efficiency. You should also tune the antenna regardless if it's a PCB or a chip antenna. The matching network should have a full Pi -network. 

regards

Jared