ST STM32H7 3 Series User Manual

DocID029918 Rev 1 11/48
AN4938 Power supplies
47
1.2 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 through 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 1.3.6: 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 decoupling 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 V
BAT
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, V
BAT
pin can be connected to V
DD
through a 100 nF external ceramic
decoupling capacitor.
• VREF+ external reference voltage for analog peripherals
V
REF+
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 μF 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, VCAP1 and VCAP2 pins must be
connected to two 2.2 µF ceramic capacitors with a low ESR (< 100 mΩ). 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.
Additional precautions can be taken to filter analog noise:
• VDDA can be connected to V
DD
through a ferrite bead.
• The VREF+ pin can be connected to V
DDA
through a resistor (typically 47 Ω).

ST STM32H7 3 Series Specifications

General

Brand	ST
Model	STM32H7 3 Series
Category	Microcontrollers
Language	English