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Functional overview STM32L476xx

24/270 DS10198 Rev 8

3.9.3 Voltage regulator

Two embedded linear voltage regulators supply most of the digital circuitries: the main

regulator (MR) and the low-power regulator (LPR).

• The MR is used in the Run and Sleep modes and in the Stop 0 mode.

• The LPR is used in Low-Power Run, Low-Power Sleep, Stop 1 and Stop 2 modes. It is

also used to supply the 32 Kbyte SRAM2 in Standby with SRAM2 retention.

• Both regulators are in power-down in Standby and Shutdown modes: the regulator

output is in high impedance, and the kernel circuitry is powered down thus inducing

zero consumption.

The ultralow-power STM32L476xx supports dynamic voltage scaling to optimize its power

consumption in run mode. The voltage from the Main Regulator that supplies the logic

CORE

) can be adjusted according to the system’s maximum operating frequency.

There are two power consumption ranges:

• Range 1 with the CPU running at up to 80 MHz.

• Range 2 with a maximum CPU frequency of 26 MHz. All peripheral clocks are also

limited to 26 MHz.

The V

CORE

can be supplied by the low-power regulator, the main regulator being switched

off. The system is then in Low-power run mode.

• Low-power run mode with the CPU running at up to 2 MHz. Peripherals with

independent clock can be clocked by HSI16.

When the MR is in use, the STM32L476xx with the external SMPS option allows to force an

external V

CORE

supply on the VDD12 supply pins.

When V

DD12

is forced by an external source and is higher than the output of the internal

LDO, the current is taken from this external supply and the overall power efficiency is

significantly improved if using an external step down DC/DC converter.

3.9.4 Low-power modes

The ultra-low-power STM32L476xx supports seven low-power modes to achieve the best

compromise between low-power consumption, short startup time, available peripherals and

available wakeup sources.

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