ST STM32F7 Series User Manual

DocID027559 Rev 5 7/54
AN4661 Power supplies
53
1 Power supplies
1.1 Introduction
The device requires a 1.8 to 3.6 V operating voltage supply (V
DD
), which can be reduced
down to 1.7 V with PDR OFF, as detailed in the product datasheets. The embedded linear
voltage regulator is used to supply the internal 1.2 V digital power.
The real-time clock (RTC), the RTC backup registers, and the backup SRAM (BKP SRAM)
can be powered from the V
BAT
voltage when the main V
DD
supply is powered off.
1.1.1 Independent A/D converter supply and reference voltage
To improve the conversion accuracy, the ADC has an independent power supply which can
be separately filtered and shielded from noise on the PCB.
• The ADC voltage supply input is available on a separate V
DDA
pin.
• An isolated supply ground connection is provided on the pin V
SSA
.
To ensure a better accuracy of low voltage inputs, the user can connect a separate external
reference voltage ADC input on V
REF
. The voltage on V
REF
ranges from 1.8 V to V
DDA
.
When available (depending on package), V
REF–
must be externally tied to V
SSA
.
1.1.2 Independent USB transceivers supply
The USB transceivers are supplied from a separated V
DDUSB
power supply pin.
The V
DDUSB
supply can be connected either to V
DD
or an external independent power
supply (3.0 to 3.6V) for the USB transceivers (refer to
Figure 1 and Figure 2). For example,
when the device is powered at 1.8V, an independent power supply 3.3V can be connected
to V
DDUSB
. When the V
DDUSB
is connected to a separated power supply, it is independent
from V
DD
or V
DDA
but it must be the last supply to be provided and the first to disappear.
The following V
DDUSB
conditions must be respected:
• During the power-on phase (V
DD
< V
DD_MIN
), V
DDUSB
should be always lower than
V
DD
.
• During the power-down phase (V
DD
< V
DD_MIN
), V
DDUSB
should be always lower than
V
DD.
• The V
DDSUB
rising and falling time rate specifications must be respected (refer to
operating conditions at power-up / power-down (regulator ON) table and operating
conditions at power-up / power-down (regulator OFF) table provided in the product
datasheet).
• In operating mode phase, V
DDUSB
could be lower or higher than V
DD:
– If USB (USB OTG_HS/OTG_FS) is used, the associated GPIOs powered by
V
DDUSB
are operating between V
DDUSB_MIN
and V
DDUSB_MAX
.
–The V
DDUSB
supplies both USB transceivers (USB OTG_HS and USB OTG_FS).
If only one USB transceiver is used in the application, the GPIOs associated to the
other USB transceiver are still supplied by V
DDUSB
.
– If USB (USB OTG_HS/OTG_FS) is not used, the associated GPIOs powered by
V
DDUSB
are operating between V
DD_MIN
and V
DD_MAX
.

ST STM32F7 Series Specifications

General

Brand	ST
Model	STM32F7 Series
Category	Microcontrollers
Language	English