Electrical characteristics
STM32F103xx
50/67
Figure 18.
I
2
C bus AC waveforms and measurement circuit
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)
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.
f
SCL
(kHz)
I2C_CCR value
R
P
= 4.7 k
Ω
400
TBD
300
TBD
200
TBD
100
TBD
50
TBD
20
TBD
ai14149b
S TART
SDA
100
Ω
4 .7 k
Ω
I
2
C bus
4 .7 k
Ω
100
Ω
VDD
VDD
STM32F103xx
SDA
SCL
tf(SDA)
tr(SDA)
SCL
th(STA)
tw(SCKH)
tw(SCKL)
tsu(SDA)
tr(SCK)
tf(SCK)
th(SDA)
S TART REPEATED
S TART
tsu(STA)
tsu(STO)
S TOP
tsu(STA:STO)