Power-On Reset (Por)/Power-Down Reset (Pdr); Brown Out Reset (Bor); Figure 13. Power-On Reset/Power-Down Reset Waveform - ST STM32L0x3 Reference Manual

Power control (PWR)
6.2.1

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

The device has an integrated POR/PDR circuitry that allows operation down to 1.5 V.
During power-on, the device remains in Reset mode when V
threshold, V
enabled and the POR threshold is 1.5 V.
During power-down, the PDR keeps the device under reset when the supply voltage (V
drops below the V
is 1.5 V.
The POR and PDR are used only when the BOR is disabled (see
reset (BOR))). To insure the minimum operating voltage (1.65 V), the BOR should be
configured to BOR Level 1. When the BOR is disabled, a "gray zone" exist between the
minimum operating voltage (1.65 V) and the V
can be lower than 1.65 V without device reset until the V
For more details concerning the power-on/power-down reset threshold, refer to the
electrical characteristics of the datasheet.
6.2.2

Brown out reset (BOR)

During power-on, the Brown out reset (BOR) keeps the device under reset until the supply
voltage reaches the specified V
For devices operating from 1.65 to 3.6 V, the BOR option is not available and the power
supply is monitored by the POR/PDR. As the POR/PDR thresholds are at 1.5 V, a "gray
zone" exists between the V
voltage 1.65 V.
For devices operating from 1.8 to 3.6 V, the BOR is always active at power-on and it's
threshold is 1.8 V.
Then when the system reset is released, the BOR level can be reconfigured or disabled by
option byte loading.
If the BOR level is kept at the lowest level, 1.8 V at power-on and 1.65 V at power-down, the
system reset is fully managed by the BOR and the product operating voltages are within
safe ranges.
150/1043
, without the need for an external reset circuit. The POR feature is always
POR
threshold. The PDR feature is always enabled and the PDR threshold
PDR

Figure 13. Power-on reset/power-down reset waveform

VDD/VDDA
POR
Reset
BOR
/V
POR PDR
RM0367 Rev 7
/V threshold. This means that V
POR PDR
PDR
Temporization
tRSTTEMPO
threshold.
thresholds and the minimum product operating
/V is below a specified
DD DDA
Section 6.2.2: Brown out
threshold is reached.
PDR
RM0367
)
DD
DD
MS32793V1