CD00237391 Datasheet, PDF (104/177 Pages) STMicroelectronics – ARM-based 32-bit MCU, 150DMIPs, up to 1 MB Flash/128+4KB RAM

Electrical characteristics
Figure 38. I²C bus AC waveforms and measurement circuit
VDD
VDD
I²C bus
4 .7 kΩ 4 .7 kΩ
100 Ω
100 Ω
STM32Fxx
SDA
SCL
STM32F20xxx
SD A
tf(SDA)
S TART
S TART REPEATED
tsu(STA)
S TART
tr(SDA)
tsu(SDA)
th(STA)
tw(SCLL)
th(SDA)
S TOP
tw(STO:STA)
SCL
tw(SCLH)
tr(SCL)
tf(SCL)
tsu(STO)
ai14979b
1. Measurement points are done at CMOS levels: 0.3V_DD and 0.7V_DD.
Table 51.
SCL frequency (f_PCLK1= 30 MHz.,V_DD = 3.3 V)⁽¹⁾⁽²⁾
f_SCL (kHz)
I2C_CCR value
R_P = 4.7 kΩ
400
0x8019
300
0x8021
200
0x8032
100
0x0096
50
0x012C
20
0x02EE
1. R_P = External pull-up resistance, f_SCL = I²C 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 ±2%. These variations depend on the accuracy of the external
components used to design the application.
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Doc ID 15818 Rev 9