Will adding a 1.8V buck converter extend the battery life of the beacon?

[Matthew K]

Hi, there~~. The PCA20006, nRF51822 Bluetooth Smart Beacon Kit, is fascinating!

So I'm planning to create a custom beacon product of my own,

a 2-layered PCB with nRF52832 using Eddystone beacon and CR2032 battery.

The schematic of PCA20006,

infocenter.nordicsemi.com/.../nRF6930_Beacon_Ref_Design_UG_v1.1.pdf

it uses the CR2032's voltage directly to power the nRF51822!

Suppose I have flashed the same smart beacon firmware to both

PCA2006 and my future custom beacon that has a buck converter to provide 1.8V and this is the only difference between those boards.

A buck converter like this one; Min input voltage = 2V, Output Max current = 50mA

www.digikey.com/.../7201124

Plus, suppose the RGB LEDs are removed so we can focus solely on beacon advertising.

Then, will this custom board run longer due to the 1.8V powered buck converter?

[Bjørn Kvaale]

The nrf52832 already has a built-in DC-DC converter. Therefore, using an extra DC-DC converter between the battery and the nrf52832 most likely will not lead to less current consumption. In addition, since the analogue parts of the nrf52832 (e.g. radio, etc.) require 1.3 V, you would need to use your DC-DC converter which converts the 3 V coin cell battery voltage down to 1.8 V plus the built-in DC-DC converter on the nrf52832. Using two DC-DC converters in series will most likely not lead to less current consumption.

If I were you, I would either do some current calculations or ideally measure current on your custom board: one scenario that uses the 3 -> 1.8 V DC-DC converter and one that does not. Most likely, adding a 3->1.8 V DC-DC converter will not lead to less current consumption and therefore will not increase the coin cell battery life.

In some situations, it can be useful to add a DC-DC converter in front of the nrf52 (e.g. giving power to multiple things that require 1.8, e.g. an accelerometer). But this is most likely not one of those cases unfortunately.

[Matthew K]

Wow! Great detailed answer, Bjørn!

You got me; I'm not trying to give power to multiple things that require 1.8V, e.g. an accelerometer.

I was trying to squeeze the last drop from the battery :D

I checked the Fig. 2, DC/DC regulator setup from your link and the schematic of PCA20014.

The PCA20014 mounted L2 and L3 at the DCC pin, just like Fig. 2.

These are my final questions;

1.How can I enable the DCDCEN register

if the supply voltage (VDD_nRF) is between 1.8~3.6V and inductors and capacitors are connected between DCC and DEC4

to use the internal DC/DC regulator?

While browsing various BLE peripheral examples, I don't see any codes related to configuring the DCDCEN register.

After getting your help, I will squeeze every last drop!

2.Due to the internal DC-DC converter, I don't have to care about the fluctuating supply voltage (VDD_nRF), right?

[Bjørn Kvaale]

Answer to 1: see these links (link1 & link2).

Answer to 2: Yes, that is correct. Just make sure that the input voltage is within the supply voltage boundaries of the nrf52832.