Power supplies AN4938
12/46 AN4938 Rev 4
2.2 Power supply scheme
Power supplies
• V
DD
= 1.62 to 3.6 V: external power supply for I/Os, Flash memory and system analog
blocks such as reset and PLL
This power supply is provided externally th
rough VDD pins. VDD pins must be
connected to V
DD
with external decoupling capacitors: one single tantalum or ceramic
capacitor (of 4.7 µF minimum capacitance) for the package and a 100 nF ceramic
capacitor for each VDD pin.
When V
DD
is lower than 1.71 V, an external reset controller is required.
Note: V
DD
minimum value of 1.62 V is obtained when the internal reset controller is OFF (refer to
Section 2.3.6: Internal reset OFF).
• V
SSA
, V
DDA
= 1.62 to 3.6 V: external analog power supplies for ADCs, DACs and
OPAMPs.
VDDA pin must be connected to two external de
coupling capacitors (100 nF ceramic
capacitors and a 1 µF tantalum or ceramic capacitor).
• V
DD33USB
and V
DD50USB
: external power supplies for USB transceiver
When VDD50USB is used to provide power, this
pin must be connected to the USB
connector VBUS line and to a 4.7 µF decoupling capacitor (C
IN
). In addition,
VDD33USB must be connected to a 1 µF capacitor and its maximum ESR should be
600 mΩ.
When VDD33USB is used to power the USB transceiver (3.0 to 3.6 V), if the
VDD50USB pin is available, it must connected to VDD33USB, which must be
connected to two external decoupling capacitors (a 100 nF ceramic capacitor and a
1 µF tantalum or ceramic capacitor).
• V
BAT
= 1.2 to 3.6 V: power supply for the RTC, the external 32 kHz oscillator and
backup registers (through power switch) when V
DD
is not present.
The VBAT pin can be connected to the external battery (1.2 V < V
BAT
< 3.6 V). If no
external battery is used, it is mandatory to connect this pin to an external power supply:
as an example, VBAT pin can be connected to V
DD
through a 100 nF external ceramic
decoupling capacitor.
• V
REF+ external reference voltage for analog peripherals
VREF+ pin can be connected to V
DDA
external power supply. If a separate external
reference voltage is applied to V
REF+
, a 100 nF and a 1 F capacitors must be
connected on this pin. In all cases, V
REF+
must be kept below V
DDA
. V
REF+
lower limit
is 2 V when V
DDA
is above 2 V and the ADC is used, otherwise it is 1.62 V.
• V
DDLDO
= 1.62 to 3.6 V: external power supply for voltage regulator
When the LDO voltage regulator is enabled, both VCAP1 and VCAP2 pins must be
conn
ected to a 2.2 µF ceramic capacitor with a low ESR (< 100 m). It is
recommended to connect VCAP1 pin to VCAP2 pin (for more details, refer to
Figure 18: STM32H753XI reference schematic).
If VCAP3 is available, it must be connected to the other VCAP pins but not additional
capacitor is required. In addition, the VDDLDOx pins must be connected together and
to a 4.7 µF tantalum or ceramic capacitor.
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