Electrical characteristics
STM32F103x4, STM32F103x6
Figure 29. I
2
C bus AC waveforms and measurement circuit
VDD
4 .7 kΩ
I²C
bus
VDD
4 .7 kΩ
100
Ω
100
Ω
STM32F10x
SDA
SCL
Start
repeated
Start
t
su(STA)
SDA
tf(SDA)
th(STA)
SCL
tw(SCLH)
tr(SCL)
tf(SCL)
t
su(STO)
ai14133d
Start
tr(SDA)
tw(SCLL)
t
su(SDA)
th(SDA)
Stop
t
su(STO:STA)
1. Measurement points are done at CMOS levels: 0.3V
DD
and 0.7V
DD
.
Table 41.
SCL frequency (f
PCLK1
= 36 MHz.,V
DD
= 3.3 V)
(1)(2)
I2C_CCR value
f
SCL
(kHz)
R
P
= 4.7 kΩ
400
300
200
100
50
20
0x801E
0x8028
0x803C
0x00B4
0x0168
0x0384
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
±
2%. These variations depend on the accuracy of the external
components used to design the application.
64/87
Doc ID 15060 Rev 5
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