nRF52840 regulators

[Daniel]

Hi, 

My team is building a wearable application similar to a smartwatch.

Our system requires two main operating voltages. 1V8 and 3V3. I was thinking that we would use a PMIC to regulate these two voltages from a battery supply. We are trying to maximize battery life on this application.

I was wondering if I could use the on-chip REG0 to regulate one of my voltages. Can I do this? Is it more efficient than using a PMIC? Which voltage should be regulated? Right now, I am thinking that I regulate the battery myself, supply 3V3 to the nRF52840 and let it regulate down to 1V8.

Please let me know,

D

[Andreas]

Hi,

 

The high-voltage input (REG0) works down to 2.5V, and can regulate the output (VDD) between VDDH-0.3V and 1.8V. What you describe should not be a problem, but bear in mind that you need to stay within the current limitation specifications. If you need to supply more current than this you need an external solution as well.

 

Best regards,

Andreas

[Daniel]

Decided to go with a PMIC to supply both rails.

I found a note in the errata for the nRF52840 describing how the first stage DC-DC regulator does not work. This would force me to use the LDO to drop from 3.3V to 1.8V. Horribly inefficient.