Power Supplies; Digital Supply; Voltage Regulator; Regulator Off Mode - ST STM32F4 Series Application Note

AN4488
2

Power supplies

The operating voltage supply (V
1.7 V with some restrictions, as detailed in the product datasheets. An embedded regulator
is used to supply the internal 1.2 V digital power.
The real-time clock (RTC), backup registers and backup registers can be powered from the
V voltage when the main V
BAT
2.1

Digital supply

2.1.1

Voltage regulator

The voltage regulator is always enabled after reset. It works in three different modes
depending on the application modes.
•
in Run mode, the regulator supplies full power to the 1.2 V domain (core, memories
and digital peripherals)
• in Stop mode, the regulator supplies low power to the 1.2 V domain, preserving the
contents of the registers and SRAM
•
in Standby mode, the regulator is powered down. The contents of the registers and
SRAM are lost except for those concerned with the Standby circuitry and the Backup
domain.
Note: Depending on the selected package, there are specific pins that should be connected either
to V or V
SS
regulator " in datasheet for details.
2.1.2

Regulator OFF mode

Refer to section "Voltage regulator" in datasheet for details.
•
When BYPASS_REG = V
and V
–
–
–
DD
to activate or deactivate the voltage regulator. Refer to section "Voltage
DD
DD
pins connected together.
CAP2
The two V ceramic capacitors should be replaced by two 100 nF decoupling
CAP
capacitors.
Since the internal voltage scaling is not managed internally, the external voltage
value must be aligned with the targeted maximum frequency.
When the internal regulator is OFF, there is no more internal monitoring on V12.
An external power supply supervisor should be used to monitor the V12 of the
logic power domain (V
) range is 1.8 V to 3.6 V, which can be reduced down to
DD
supply is powered off.
, the core power supply should be provided through V
).
CAP
AN4488 Rev 7
Power supplies
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