ST STM32L4+ Series Reference Manual page 188

Power control (PWR)
preserved (depending on RRS[1:0] bits in the PWR_CR3 register). The main regulator
(MR) is off and the low-power regulator (LPR) provides the supply only to SRAM2. The
core, digital peripherals (except Standby circuitry and backup domain) and SRAM1 are
powered off.
Note: For STM32L4Rxxx and STM32L4Sxxx devices it is only possible to preserve the full
SRAM2 content depending on RRS bit in the PWR_CR3 register. For STM32L4P5xx and
STM32L4Q5xx devices it is possible to preserve the full (64 Kbytes) or partial (4 Kbytes)
SRAM2 content depending on RRS[1:0] bits in the PWR_CR3 register.
•
In Standby mode, both regulators are powered off. The contents of the registers,
SRAM1, SRAM2 and SRAM3 is lost except for the Standby circuitry and the backup
domain.
• In Shutdown mode, both regulators are powered off. When exiting from Shutdown
mode, a power-on reset is generated. Consequently, the contents of the registers,
SRAM1, SRAM2 and SRAM3 is lost, except for the backup domain.
5.1.7 VDD12 domain
VDD12 is intended to be connected with external SMPS (switched-mode power supply) to
generate the V
VDD12 pins correspond to the internal V
FLASH and peripherals. This significantly improves the power consumption with a gain from
50% or more depending of the SMPS performances.
The main benefit occurs in Run and Sleep modes whereas in Stop 0 mode, the gain is less
significant.
The figure below shows a schematic to understand how the internal regulator stops
supplying V
As VDD12 shares the same pin as output of the internal regulator, applying a slightly higher
voltage (typically +50 mV) on the VDD12 blocks, the PMOS and the regulator consumption
is negligible.
A switch, controlled by the chosen GPIO, is inserted between the SMPS output and VDD12.
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logic supply in Run, Sleep and Stop 0 modes only.
CORE
when an external voltage VDD12 is provided.
CORE
Figure 11. Internal main regulator overview
Switch
VDD12
Vsmps
RM0432 Rev 6
powering the digital part of Core, RAMs,
CORE
VDD
PMOS
V
CORE
Voltage regulator
Ref
RM0432
MSv44809V1