Electrical characteristics
STM32F105xx, STM32F107xx
5.3.15
Communications interfaces
I2C interface characteristics
Unless otherwise specified, the parameters given in Table 40 are derived from tests
frequency and V supply voltage
DD
performed under the ambient temperature, f
conditions summarized in Table 9.
PCLK1
2
I
The STM32F105xx and STM32F107xx C interface meets the requirements of the
2
standard I C communication protocol with the following restrictions: the I/O pins SDA and
SCL are mapped to are not “true” open-drain. When configured as open-drain, the PMOS
connected between the I/O pin and V is disabled, but is still present.
DD
2
The I C characteristics are described in Table 40. Refer also to Section 5.3.12: I/O port
for more details on the input/output alternate function characteristics (SDA
characteristics
and SCL)
.
2
Table 40. I C characteristics
Standard mode I2C(1)
Fast mode I2C(1)(2)
Symbol
Parameter
Unit
Min
Max
Min
Max
tw(SCLL)
tw(SCLH)
tsu(SDA)
th(SDA)
SCL clock low time
SCL clock high time
SDA setup time
4.7
4.0
1.3
0.6
µs
250
0(3)
100
0(4)
SDA data hold time
900(3)
300
tr(SDA)
tr(SCL)
ns
SDA and SCL rise time
1000
300
20 + 0.1Cb
tf(SDA)
tf(SCL)
SDA and SCL fall time
Start condition hold time
300
th(STA)
tsu(STA)
4.0
4.7
4.0
4.7
0.6
0.6
0.6
1.3
µs
Repeated Start condition
setup time
tsu(STO)
Stop condition setup time
os
os
Stop to Start condition time
(bus free)
tw(STO:STA)
Capacitive load for each bus
line
Cb
400
400
pF
Guaranteed by design, not tested in production.
1.
2. fPCLK1 must be higher than 2 MHz to achieve the maximum standard mode I2C frequency. It must be
higher than 4 MHz to achieve the maximum fast mode I2C frequency.
The maximum hold time of the Start condition has only to be met if the interface does not stretch the low
period of SCL signal.
3.
The device must internally provide a hold time of at least 300ns for the SDA signal in order to bridge the
undefined region of the falling edge of SCL.
4.
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