RE: nRF52833/52840 reset pin in brownout

xgroleau — Tue, 07 Apr 2026 17:37:10 GMT

Hi Priyanka,

We've been experiencing something similar with the nRF52833, it seems that when we are using the internal DCDC.
We can't recover from a brownout when lowering VDD to about 1.6V, raising back the voltage the chip doesn't startup, we are unabled to connect a debugger to the chip and a reset doesn't seem to fix it. Note that we are not using high voltage mode in this product.

Disabling the DCDC and using the LDO instead seems to solve the issue, but I'm not conviced if that just makes it less likely or actually solves the problem.

If internal DCDC enabled

Power starts at 1.8V
Lower power source at 1.6V: brown out
1.85V Still not alive, need complete power cycle to start properly

If internal DCDC disabled (thus using LDO

Power starts at 1.8V
Lower power source at 1.6V: brown out
1.65V Comes back and the MCU starts properly

Before issuing that fix to our customers I would like to confirm if that is an actual fix or that just makes the issue less likely. Also if that is a known/reproducible and what is the source of the issue in the nRF, if it's an issue with the startup power path or something else.

Thank you
Xavier

RE: nRF52833/52840 reset pin in brownout

Priyanka — Tue, 07 Oct 2025 12:41:24 GMT

Hi Dominic,

Apologies for the delayed response. If you power the chip through VDDH (High-Voltage mode), the BOR comparator still watches the internal VDD (REG0 output), not VDDH. So the internal VDD may still be <1.6 V on the nRF52833 (e.g., regulator hasn’t restarted yet, or is loaded), so BOR is still asserted. Could you check the actual VDD pin at the SoC and not just the 3.3/3.6 V rail ?

-Priyanka