Power Supply Supervisor; Power-On Reset (Por)/Power-Down Reset (Pdr); Brownout Reset (Bor); Figure 9. Power-On Reset/Power-Down Reset Waveform - ST STM32F40 Series Reference Manual

RM0090
5.2

Power supply supervisor

5.2.1

Power-on reset (POR)/power-down reset (PDR)

The device has an integrated POR/PDR circuitry that allows proper operation starting from
to 1.8 V.
The device remains in Reset mode when V
V
POR/PDR
power on/power-down reset threshold, refer to the electrical characteristics of the datasheet.
Figure 9.
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
V is configured through device option bytes. By default, BOR is off. 4 programmable
BOR
V thresholds can be selected.
BOR
●
BOR off (V
●
BOR Level 1 (V
●
BOR Level 2 (V
●
BOR Level 3 (V
When the supply voltage (V
generated.
BOR can be disabled by programming the device option bytes. To disable the BOR function,
V must have been higher than V
DD
sequence. The power-down is then monitored by the PDR (see
reset (POR)/power-down reset
, without the need for an external reset circuit. For more details concerning the
Power-on reset/power-down reset waveform
VDD/VDDA
PDR
Reset
): reset threshold level for 1.8 to 2.10 V voltage range
BOR0
): reset threshold level for 2.10 to 2.40 V voltage range
BOR1
): reset threshold level for 2.40 to 2.70 V voltage range
BOR2
): reset threshold level for 2.70 to 3.60 V voltage range
BOR3
) drops below the selected V
DD
Doc ID 018909 Rev 4
/V is below a specified threshold,
DD DDA
40 mV
hysteresis
Temporization
tRSTTEMPO
threshold.
BOR
to start the device option byte programming
BOR0
(PDR))
Power controller (PWR)
PDR
threshold, a device reset is
BOR
Section 5.2.1: Power-on
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