Power Supplies; Introduction; Independent Analog Supply And Reference Voltage; Usb Transceiver Independent Power Supply - ST STM32H7 3 Series Application Note

AN4938
1

Power supplies

1.1

Introduction

STM32H743/753xx devices require a 1.71 to 3.6 V operating voltage supply (V
can be reduced down to 1.62 V by using an external power supervisor and connecting
PDR_ON pin to V
The digital power can be supplied either by a internal linear voltage regulator or directly by
an external supply voltage. This digital power voltage can be set dynamically at different
values ranging from 0.7 to 1.2 V, the highest value allowing to achieve the maximum
performance.
The real-time clock (RTC), the RTC backup registers, and the backup SRAM (BKP SRAM)
can be powered from the V
OFF.
1.1.1

Independent analog supply and reference voltage

To improve analog peripheral performance, the analog peripherals feature an independent
power supply which can be separately filtered and shielded from noise on the PCB:
•
The analog supply voltage input is available on a separate VDDA pin.
•
An isolated supply ground connection is provided on the pin V
To ensure a better accuracy of low-voltage inputs, the user can connect a separate external
reference voltage on V
When available (depending on the package), V
V minimum value (V
DDA
reference voltage is provided or not:
•
If no analog peripheral is used, V
•
When an ADC or a comparator is used, V
•
When a DAC is used, V
•
When an OPAMP is used, V
•
When a reference voltage (VREFBUF_OUT) is provided by the device on V
V
DDA_MIN
1.1.2

USB transceiver independent power supply

There are different ways to supply the USB transceivers, depending on V
V
DD50USB
•
When the VDD50USB pin is available, this pin can be used to supply an internal
regulator dedicated to USB transceivers. In this case, VDD50USB pin should receive a
voltage ranging from 4.0 to 5.5 V, typically supplied from the VBUS line of the USB
connector. The regulated power (3.0 to 3.6 V) is available on VDD33USB.
In this configuration V
supply (see
An external capacitor must be connected to VDD33USB.
(refer to the datasheets for details).
SS
voltage (1.2 to 3.6 V) when the main V
BAT
. The voltage applied to V
REF+
DDA_MIN
DDA_MIN
depends on the required level for this voltage.
availability:
DD50USB
Figure 3).
DocID029918 Rev 1
REF+
pin must be externally tied to V
REF–
) depends on the analog peripheral and on whether a
equals 0 V.
DDAmin
DDA_MIN
equals 1.8V.
equals 2.0 V.
DDA_MIN
voltage can rise indifferently after or before V
Power supplies
supply is powered
DD
.
SSA
ranges from 1.8 V to V
equals 1.62 V.
DD33USB
), which
DD
.
DDA
.
SSA
pin,
REF+
and
power
DD
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