SM72442 Datasheet, PDF (12/14 Pages) National Semiconductor (TI) – Programmable Maximum Power Point Tracking Controller for Photovoltaic Solar Panels

FIGURE 12. I2C Write Sequence
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Noise coupling into digital lines greater than 400 mVp-p (typ-
ical hysteresis) and undershoot less than 500 mV GND, may
prevent successful I2C communication with SM72442. I2C no
acknowledge is the most common symptom, causing unnec-
essary traffic on the bus although the I2C maximum frequency
of communication is rather low (400 kHz max), care still needs
to be taken to ensure proper termination within a system with
multiple parts on the bus and long printed board traces. Ad-
ditional resistance can be added in series with the SDA and
SCL lines to further help filter noise and ringing. Minimize
noise coupling by keeping digital races out of switching power
supply areas as well as ensuring that digital lines containing
high speed data communications cross at right angles to the
SDA and SCL lines.
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