Usb Vbus Example; I/O Usage For The Five-Volt Adc Conversion; Figure 11. Example Of Usb Vbus Connections; Figure 12. Example Of Vbus To Vdd Power Supply - ST STM32 Application Note

AN4899
5.3.5

USB VBUS example

The VBUS pad of STM32 devices is five-volt tolerant, However, it needs to comply with the
V maximum rating. If STM32 is supplied from an independent supply, it is not allowed to
DD
connect VBUS as long as STM32 is not supplied. Another solution is to place a Zenner
diode (ex. 3.3 V) between VBUS and V
V
If the STM32 supply is provided by an LDO supplied by VBUS, it is recommended to use a
Zenner diode (ex. 3.3 V) as illustrated in
V = 5 V
BUS
5.3.6

I/O usage for the five-volt ADC conversion

STM32 devices have FT pads which are connected to ADC input. When ADC is not
connected (analog switch in I/O is not closed), the I/O can accept V
situation, 5 V applied to FT pad can be granted.
However, once the I/O input is connected to the ADC, and during the sampling phase, the
parasitic diode to V

Figure 11. Example of USB VBUS connections

= 3.3 V
DD
STM32
Figure 12. Example of V
3.3 V
(example)
and/or VREF+ is forward biased as shown in
DDA
GPIO electrical characteristics and definitions
as illustrated in
DD
3.3 V
(example)
Figure 12.
to V
BUS DD
LDO
AN4899 Rev 3
Figure 11.
VBUS
D+ D+
D-
GND
power supply
V = 3.3 V
DD
To STM32 VDD
+ 3.6 V. In this
DD
Figure 13.
MSv46882V1
MSv46883V1
21/31
30