Electrical characteristics
Figure 18. I2C bus AC waveforms and measurement circuit
VDD
VDD
I2C bus
4 .7 kΩ 4 .7 kΩ
100Ω
100Ω
STM32F103xx
SDA
SCL
STM32F103xx
SD A
tf(SDA)
S TART
S TART REPEATED
tsu(STA)
S TART
tr(SDA)
tsu(SDA)
th(STA)
tw(SCKL)
th(SDA)
S TOP
tsu(STA:STO)
SCL
tw(SCKH)
tr(SCK)
tf(SCK)
tsu(STO)
ai14149b
1. Measurement points are done at CMOS levels: 0.3VDD and 0.7VDD.
Table 35.
SCL frequency (fPCLK1= 36 MHz.,VDD = 3.3 V)(1)(2)(3)
fSCL (kHz)
I2C_CCR value
RP = 4.7 kΩ
400
TBD
300
TBD
200
TBD
100
TBD
50
TBD
20
TBD
1. TBD = to be determined.
2. RP = External pull-up resistance, fSCL = I2C speed,
3. 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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