Datasheet

DS9716 Rev 11 19/139
STM32F401xB STM32F401xC Functional overview
53
3.14 Power supply supervisor
3.14.1 Internal reset ON
This feature is available for V
DD
operating voltage range 1.8 V to 3.6 V.
The internal power supply supervisor is enabled by holding PDR_ON high.
The devices have an integrated power-on reset (POR) / power-down reset (PDR) circuitry
coupled with a Brownout reset (BOR) circuitry. At power-on, POR is always active, and
ensures proper operation starting from 1.8 V. After the 1.8 V POR threshold level is
reached, the option byte loading process starts, either to confirm or modify default
thresholds, or to disable BOR permanently. Three BOR thresholds are available through
option bytes.
The devices remain in reset mode when V
DD
is below a specified threshold, V
POR/PDR
or
V
BOR
, without the need for an external reset circuit.
The devices also feature an embedded programmable voltage detector (PVD) that monitors
the V
DD
/V
DDA
power supply and compares it to the V
PVD
threshold. An interrupt can be
generated when V
DD
/V
DDA
drops below the V
PVD
threshold and/or when V
DD
/V
DDA
is
higher than the V
PVD
threshold. The interrupt service routine can then generate a warning
message and/or put the MCU into a safe state. The PVD is enabled by software.
3.14.2 Internal reset OFF
This feature is available only on packages featuring the PDR_ON pin. The internal power-on
reset (POR) / power-down reset (PDR) circuitry is disabled by setting the PDR_ON pin to
low.
An external power supply supervisor has to monitor V
DD
and keep the device in reset mode
as long as V
DD
is below a specified threshold. Connect PDR_ON to this external power
supply supervisor. Refer to Figure 5.
Figure 5. Power supply supervisor interconnection with internal reset OFF
(1)
1. The PRD_ON pin is only available on the WLCSP49 and UFBGA100 packages.
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