Electrical characteristics
Figure 18. I
2
C bus AC waveforms and measurement circuit
VDD
4 .7 kΩ
I
2
C bus
VDD
4 .7 kΩ
STM32F103xx
SDA
100Ω
SCL
STM32F103xx
100Ω
S TART REPEATED
S TART
tsu(STA)
SDA
tf(SDA)
th(STA)
SCL
tw(SCKH)
S TART
tr(SDA)
tw(SCKL)
tsu(SDA)
th(SDA)
S TOP
tsu(STA:STO)
tr(SCK)
tf(SCK)
tsu(STO)
ai14149b
1. Measurement points are done at CMOS levels: 0.3V
DD
and 0.7V
DD
.
Table 35.
SCL frequency (f
PCLK1
= 36 MHz.,V
DD
= 3.3 V)
(1)(2)(3)
I2C_CCR value
f
SCL
(kHz)
R
P
= 4.7 kΩ
400
300
200
100
50
20
TBD
TBD
TBD
TBD
TBD
TBD
1. TBD = to be determined.
2. R
P
= External pull-up resistance, f
SCL
= I
2
C 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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