Electrical characteristics
STM32F103xC, STM32F103xD, STM32F103xE
Figure 48. I
2
C bus AC waveforms and measurement circuit
VDD
4 .7 k
I
2
C bus
4 .7 k
VDD
STM32F103xx
SDA
100
SCL
100
S TART REPEATED
S TART
tsu(STA)
SDA
tf(SDA)
th(STA)
SCL
tw(SCLH)
tr(SDA)
tw(SCLL)
tsu(SDA)
th(SDA)
S TOP
tw(STO:STA)
S TART
tr(SCL)
tf(SCL)
tsu(STO)
ai14149c
1. Measurement points are done at CMOS levels: 0.3V
DD
and 0.7V
DD
.
Table 52.
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.
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Doc ID 14611 Rev 8
STMICROELECTRONICS [ STMICROELECTRONICS ]
