Power-On Reset (Por)/Power-Down Reset (Pdr), Brownout Reset (Bor); Programmable Voltage Detector (Pvd); Figure 4. Power On Reset/Power Down Reset Waveform - ST STM32L152-EVAL Application Note

AN3216
2.3.1 Power-on reset (POR)/power-down reset (PDR),
brownout reset (BOR)
The monitoring voltage begins at 0.7 V.
During power-on, for devices operating between 1.8 and 3.6 V, the BOR keeps the device
under reset until the supply voltages (V
voltage (1.8 V). At power-up this internal reset is maintained during ~1 ms to wait for the
supply to reach its final value and stabilize.
At power-down the reset is activated as soon as the power drops below the lowest limit
(1.65 V).
At power-on, a defined reset should be maintained below 0.7 V. The upper threshold for a
reset release is defined in the electrical characteristics section of the product datasheets.
Figure 4.
Reset
If you want to run the cpu at full speed the threshold should be raised to 2.0 V. For a
programmable threshold above the chip lowest limit, a brownout reset can be configured to
the desired value. The BOR can also be used to detect a power voltage drop earlier. The
threshold values of the BOR can be configured through the FLASH_OBR option byte.
2.3.2

Programmable voltage detector (PVD)

The device features an embedded programmable voltage detector (PVD) that monitors the
V /V
DD DDA
can be selected by software between 1.85 V and 3.05 V, with a 200 mV step. An interrupt
can be generated when V
is higher than the V
message and/or puts the MCU into a safe state. The PVD is enabled by software
configuration. As an example, the service routine can perform emergency shutdown tasks.
Power on reset/power down reset waveform
V /V
DD DDA
POR
power supply and compares it to the V
/V
DD DDA
threshold. The interrupt service routine then generates a warning
PVD
Doc ID 17496 Rev 5
and V ) come close to the lowest acceptable
DD DDIO
Temporization
t
RSTTEMPO
threshold. Seven different PVD levels
PVD
drops below the V
PVD
Power supplies
PDR
threshold and/or when V /V
DD DDA
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