Electrical characteristics
STM32L151xC STM32L152xC
92/135
DocID022799 Rev 10
Figure 21. I
2
C bus AC waveforms and measurement circuit
1. R
S
= series protection resistor.
2. R
P
= external pull-up resistor.
3. V
DD_I2C
is the I2C bus power supply.
4. Measurement points are done at CMOS levels: 0.3V
DD
and 0.7V
DD.
Table 49. SCL frequency (f
PCLK1
= 32 MHz, V
DD
= V
DD_I2C
= 3.3 V)
(1)(2)
1. R
P
= External pull-up resistance, f
SCL
= I
2
C speed.
2. For speeds around 200 kHz, the tolerance on the achieved speed is of
±
5%. For other speed ranges, the
tolerance on the achieved speed is
±
2%. These variations depend on the accuracy of the external
components used to design the application.
f
SCL
(kHz)
I2C_CCR value
R
P
= 4.7 k
Ω
400
0x801B
300
0x8024
200
0x8035
100
0x00A0
50
0x0140
20
0x0320
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