Battery optimization for nrf52832

[Ricky A. Rosa]

Hello,

I have a battery with 4.2v max charge. Since this is outside the input range for nrf52832, I have to add a down voltage regulator. Now the question is: Should I down regulate it to 3.3 or 1.8v?

I have to drive an RBG LED that requires more than 3.3v but I would also like to extend the battery life as much as possible. I found this solution to drive nrf at 1.8v and boost the voltage using PWM to drive the LED: 

https://devzone.nordicsemi.com/f/nordic-q-a/75124/is-this-robust-nrf52840-1-8v-low-power-mode-driving-rgb-led-from-3-3v

But I would like to avoid the extra components if possible. So my question is: would down regulating to 1.8v instead of 3.3v help to substantially increase battery life given that the DCDC on the nrf52832 is enabled?

I found this post that says it doesn't but the argument here is that the coin cell is already within range so there's no need for external down regulating. 

https://devzone.nordicsemi.com/f/nordic-q-a/25919/will-adding-a-1-8v-buck-converter-extend-the-battery-life-of-the-beacon 

In this case there is a need for down regulating since the battery we're using goes to up to 4.2v. The LED will be used scarcely. Should I boost the 1.8v with PWM or should I just go with 3.3v? Does the amount of battery life gain justify the added components?

Best,

Ricky

[Simonr]

Hi again

Does the external regulator have to be a DCDC regulator? I think you would gain most from using an LDO for example to get down to 3.3V, and then use the internal DCDC on the nRF52 for the best current consumption. It should still be good with an external DCDC as well, and use the internal DCDC on the nRF52. You won't gain anything from going down to 1.8V with the internal DCDC.

Best regards,

Simon