Power controller (PWR) RM0402
86/1163 RM0402 Rev 6
5 Power controller (PWR)
5.1 Power supplies
There are two main power supply schemes:
• VDD = 1.7 to 3.6 V: external power supply for I/Os with the internal regulator disabled,
provided externally through VDD pins. Requires the use of an external power supply
supervisor connected to the VDD and PDR_ON pins.
• VDD = 1.8 to 3.6 V: external power supply for I/Os and the internal regulator (when
enabled), provided externally through VDD pins.
• V
DD_USB
= 3.0 to 3.6 V
V
DD_USB
is a dedicated independent USB power supply for full speed transceivers.
Note: V
DD_USB
value does not dependent on V
DD
and V
DDA
. However, V
DD_USB
must be the last
supply to be delivered to the device and the first to be switched off. When the three power
supplies are shut down, if V
DD_USB
remains active for a short period of time and V
DDA
/V
DDIO
fall below the functional range, the device is not be damaged.
The device is still functional when V
DD_USB
is switched off.
The real-time clock (RTC), and the RTC backup registers can be powered from the V
BAT
voltage when the main V
DD
supply is powered off.
Note: Depending on the operating power supply range, some peripheral may be used with limited
functionality and performance. For more details refer to section "General operating
conditions" in the datasheet.
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