4.4 Effects from Mixed Signal I/O

When using mixed signal I/O in the microcontroller with analog inputs, there are parasitic effects created by the I/O pads. The two biggest parasitics to consider are input capacitance and Electro-Static Discharge (ESD) diode leakage. The leakage through the ESD diodes is not Input Bias Current, which is the current entering or exiting the operational amplifier, but from a high-level view, the effect is similar. In some cases, the leakage through the ESD diodes may exceed the leakage from the input bias current. Higher operating temperatures will cause significantly higher current leakage than cooler temperatures.