2.5 Slew Rates

The slew rate determines how fast I/O can change state, from 0 to 1 (rising) and 1 to 0 (falling). Slew rate is critical for open-drain serial communication, like I²C. If the slew rate is too low, it may not work correctly. The slew rate problems in I²C are usually caused by weak pull-up resistors or high bus capacitance.

Figure 2-3. Comparison of a Properly Operating I²C bus (top) Versus an Incorrect Implementation (bottom)

In general, I²C is not suitable for long wiring runs due to these limitations. However, one can use specialized interface devices on the market to extend I²C over long distances.