Uart Application; Figure 9. Example Of 5 V To 3.3 V Power Supply; Figure 10. Example Of Uart Connections - ST STM32 Application Note

GPIO electrical characteristics and definitions
In the example shown in
V = 5 V
DDX
5.3.4

UART application

If the UART transceiver to communicate with is supplied with TTL-compatible 5 V, the
STM32 device can directly communicate as shown in
V
If the 5 V UART interface input is TTL compatible, V
that a 3.3 V CMOS output can drive without any problem. An STM32 FT pad can accept 0 V
to 5 V CMOS level input when V
20/31
Figure

Figure 9. Example of 5 V to 3.3 V power supply

3.3 V
(example)
LDO

Figure 10. Example of UART connections

= 3.3 V
DD
STM32
UART TX
TTL / CMOS compatible
UART RX
GND
9, V is the output of the LDO supplied by V
DD
UART TRX
charge pump
OL
= 3.3 V.
DD
AN4899 Rev 3
V = 3.3 V
DD
To STM32 VDD
Figure 10.
V = 5 V
DD
with
+/-12 V
+/-12 V
GND
< 0.8 V and V > 2.0 V. This implies
OH
AN4899
.
DDX
MSv46880V1
MSv46881V1