RM0090: Reference manual - STMicroelectronics

RM0090 Power control (PWR)
5.2.2 Brownout reset (BOR)
During power on, the Brownout reset (BOR) keeps the device under reset until the supply
voltage reaches the specified V BOR threshold.
VBOR is configured through device option bytes. By default, BOR is off. 4 programmable
VBOR thresholds can be selected.
● BOR off (VBOR0 ): reset threshold level for 1.8 to 2.10 V voltage range
● BOR Level 1 (VBOR1 ): reset threshold level for 2.10 to 2.40 V voltage range
● BOR Level 2 (VBOR2 ): reset threshold level for 2.40 to 2.70 V voltage range
● BOR Level 3 (VBOR3 ): reset threshold level for 2.70 to 3.60 V voltage range
When the supply voltage (VDD ) drops below the selected VBOR threshold, a device reset is
generated.
BOR can be disabled by programming the device option bytes. To disable the BOR function,
VDD must have been higher than VBOR0 to start the device option byte programming
sequence. The power-down is then monitored by the PDR (see Section 5.2.1: Power-on
reset (POR)/power-down reset (PDR))
The BOR threshold hysteresis is ~100 mV (between the rising and the falling edge of the
supply voltage).
Figure 10. BOR thresholds
VDD/VDDA
Reset
BOR threshold
5.2.3 Programmable voltage detector (PVD)
100 mV
hysteresis
MS30432V1
You can use the PVD to monitor the VDD power supply by comparing it to a threshold
selected by the PLS[2:0] bits in the PWR power control register (PWR_CR) for STM32F40x
and STM32F41x and PWR power control register (PWR_CR) for STM32F42x and
STM32F43x.
The PVD is enabled by setting the PVDE bit.
Doc ID 018909 Rev 3 96/1416