Datasheet
Electrical characteristics STM32L452xx
174/210 DocID029968 Rev 3
6.3.25 Communication interfaces characteristics
I
2
C interface
characteristics
The I2C interface meets the timings requirements of the I
2
C-bus specification and user
manual rev. 03 for:
• Standard-mode (Sm): with a bit rate up to 100 kbit/s
• Fast-mode (Fm): with a bit rate up to 400 kbit/s
• Fast-mode Plus (Fm+): with a bit rate up to 1 Mbit/s.
The I2C timings requirements are guaranteed by design when the I2C peripheral is properly
configured (refer to RM0394 reference manual).
The SDA and SCL I/O requirements are met with the following restrictions: the SDA and
SCL I/O pins are not “true” open-drain. When configured as open-drain, the PMOS
connected between the I/O pin and V
DDIOx
is disabled, but is still present. Only FT_f I/O pins
support Fm+ low level output current maximum requirement. Refer to
Section 6.3.14: I/O
port characteristics for the I2C I/Os characteristics.
All I2C SDA and SCL I/Os embed an analog filter. Refer to the table below for the analog
filter characteristics:
Table 91. IWDG min/max timeout period at 32 kHz (LSI)
(1)
1. The exact timings still depend on the phasing of the APB interface clock versus the LSI clock so that there
is always a full RC period of uncertainty.
Prescaler divider PR[2:0] bits
Min timeout RL[11:0]=
0x000
Max timeout RL[11:0]=
0xFFF
Unit
/4 0 0.125 512
ms
/8 1 0.250 1024
/16 2 0.500 2048
/32 3 1.0 4096
/64 4 2.0 8192
/128 5 4.0 16384
/256 6 or 7 8.0 32768
Table 92. WWDG min/max timeout value at 80 MHz (PCLK)
Prescaler WDGTB Min timeout value Max timeout value Unit
1 0 0.0512 3.2768
ms
2 1 0.1024 6.5536
4 2 0.2048 13.1072
8 3 0.4096 26.2144
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