VDDH lesser than VDD_REG_OUT

[Akash.S]

Hi,

I am using nRF52840 dongle. The REG_OUT is programmed to 3.3V by default. 

I am planning to use Li ion battery at VDDH. When the battery discharges below 3.3V, is there any auto cut off feature inside nRF52840.

If not, would the low voltage (say 3V) damage the module (due to higher currents drawn for RF power requirements)?

[Marjeris Romero]

is there any auto cut off feature inside nRF52840.

No. VDDH mininum supply voltage is of 2.5V, so 3V will still be inside the specs. But in high voltage mode the configured output voltage for REG0 must not be greater than REG0 input voltage minus the voltage drop in REG0 (VDDH-Vvddh-vdd). So VDDH > VDD + 0.3V, you will need to configure REGOUT0 to 2.7V or lower.

Also make sure you check you are inside the maximum allowed current drawn by external circuitry specification. The maximum current that can be dawn externally from REG0 is defined in Regulator specifications, REG0 stage.

Personally I don't recommend to connect VDDH  directly to your Li-ion battery directly but make your own battery management circuit. There are some power manager ICs in the market that can be handy for doing this if you don't want to design your own battery charging circuit, for instance nPM1100.

Best regards,

Marjeris