Change brownout reset voltage

My F4 based FC does not seem to run below 3.3V. Is there any brownout reset or another voltagebased powermanagement feature of the stm32f4 enabled? I could not find anything obvious in the HAL librarys. Does ChibiOS handle this feature?

EDIT: I have to clarify: I want to use the FC using less than 3.3V. The stm32f4 chip and all sensors are (based on their datasheets) happy with at least 2.5V. I want to use the FC with voltages down to 2.5V, therefore I need the MCU not to reset (and stay off) below 3.3V.

You might need to add a small 5v buck converter to keep the voltage stable.