What to Do with Unused IC Pins
When working with integrated circuits, unused pins are often left behind. These pins can cause unexpected circuit operation or even damage the integrated circuit itself. This can also result in increased power consumption and, as a result, rapid battery or cell discharge. Therefore, it's important to handle unused pins on integrated circuits properly. In some cases, the pins can be left as is, in others, they need to be connected to the positive or negative terminal of the power source, and in others, they must not be connected anywhere.
Unused pins on CMOS integrated circuits must be connected to the positive or negative terminal of the power source, as the main components of such integrated circuits are insulated-gate field-effect transistors (IGFETs). A GFET pin can be thought of as a mini-antenna that picks up various electromagnetic waves. This causes charges to accumulate on the gate of the GFET, and when a certain potential is reached, a breakdown of the dielectric layer can occur. Ultimately, the transistor, and consequently the integrated circuit, will fail. In CMOS logic gates, only the gate inputs should be connected to positive or ground. The output pin should be left as is, as it is guaranteed to be high or low, determined by the type of logic gate and the state of the inputs. Connecting the output pin may cause a short circuit.
The inputs of an unused comparator should be supplied with opposite potentials, that is, either positive-negative or negative-positive, but not the same potential.
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