Datasheet
Electrical characteristics STM32H743xI
180/226 DocID030538 Rev 3
6.3.32 Communications interfaces
I
2
C interface
characteristics
The I
2
C interface meets the timings requirements of the I
2
C-bus specification and user
manual rev. 03 for:
• Sta
ndard-mode (Sm): with a bit rate up to 100 kbit/s
• Fast-mode (Fm): with a bit rate up to 400 kbit/s.
• Fast-mode Plus (Fm+): with a bit rate up to 1Mbit/s.
The I
2
C timings requirements are guaranteed by design when the I2C peripheral is properly
configured (refer to RM0433 reference manual) and when the i2c_ker_ck frequency is
greater than the minimum shown in the table below:
The SDA and SCL I/O requirements are met with the following restrictions:
• Th
e SDA and SCL I/O pins are not “true” open-drain. When configured as open-drain,
the PMOS connected between the I/O pin and V
DD
is disabled, but is still present.
• The 20 mA output drive requirement in Fast-mode Plus is not supported. This limits the
maximum load C
load
supported in Fm+, which is given by these formulas:
t
r(SDA/SCL)
=0.8473xR
p
xC
load
R
p(min)
= (V
DD
-V
OL(max)
)/I
OL(max)
Where R
p
is the I2C lines pull-up. Refer to
Section 6.3.15: I/O port characteristics
for the
I2C I/Os characteristics.
All I
2
C SDA and SCL I/Os embed an analog filter. Refer to Table 101 for the analog filter
characteristics:
Table 100. Minimum i2c_ker_ck frequency in all I2C modes
Symbol Parameter Condition Min Unit
f(I2CCLK)
I2CCLK
frequency
Standard-mode 2
MHz
Fast-mode
Analog filter ON
DNF=0
8
Analog filter OFF
DNF=1
9
Fast-mode Plus
Analog filter ON
DNF=0
17
Analog filter OFF
DNF=1
16
Table 101. I2C analog filter characteristics
(1)
1. Guaranteed by design.
Symbol Parameter Min Max Unit
t
AF
Maximum pulse width of spikes that
are suppressed by the analog filter
50
(2)
2. Spikes with widths below t
AF(min)
are filtered.
260
(3)
3. Spikes with widths above t
AF(max)
are not filtered.
ns
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