AN4365 datasheet(10/35 Pages) STMICROELECTRONICS

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STM32F4 power consumption

AN4365

10/35

DocID025303 Rev 2

STM32F4 MCUs offer the following scales:

•

STM32F427x/437x/429x/439x: three voltage scales

–

scale3 (up to 120 MHz)

–

scale2 (from 120 to 144 MHz)

–

scale1 (up to 180 MHz)

•

STM32F405x/415x/407x/417x: two voltage scales

–

scale2 (up to 144 MHz)

–

scale1 (up to 168 MHz)

•

STM32F401x: two voltage scales

–

scale3 (up to 60 MHz)

–

scale2 (up to 84 MHZ)

1.2.3

Voltage regulator bypass

This feature consists in using an external source for the CPU core voltage instead of an

internal LDO regulator voltage output. When bypassing the voltage regulator, we can save

up to 50% of power when the supply voltage is 3.3 V and up to 35% in case when the supply

voltage is 1.8 V.

1.2.4

Voltage regulator power tricks

There are new tricks implemented in STM32F4 MCUs to reduce current consumption by

monitoring the regulator voltage output.

•

Over-drive mode: this mode allows the CPU and the core logic to operate at a higher

frequency than the normal mode for a given voltage scaling (scale1, scale2 or scale3).

This mode is available only with STM32F429x/439x devices.

•

Low-voltage mode: in Stop mode, we can further reduce the voltage output of the low-

power regulator by using the Low-voltage mode. This mode is only available in Stop

mode with STM32F429x/439x and STM32F401x devices.

•

Under-drive mode: the 1.2 V domain is preserved in Reduced-leakage mode. This

mode is only available in Stop mode when the main regulator or the low-power

regulator is in Low-voltage mode. Under-drive mode is available only with

STM32F429x/439x devices.

1.2.5

ART configuration

The ART accelerator implements an instruction prefetch queue and instruction/data caches,

which increase the overall system performance speed and efficiency by increasing the

Flash memory access.

When the user does not need the system’s full processing performance and wants to further

reduce the consumption, it is recommended to disable the prefetch buffer by software.

Disabling the prefetch buffer avoids extra Flash access that consumes almost up to 10% of

the overall consumption without affecting much the overall performance, depending on the

code alignment on the Flash memory.

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