If I'm using an IC in the 74HC or 74HCT family, and I'm not using all the input pins, I understand that I should not leave them unconnected because they will float. But what exactly should I do with them, and what are the pros and cons of the different options?
For example, if I'm using the 74HCT08, which has four AND gates, and I'm only using two of the gates, what should I do with the inputs of the other two gates?
I've seen various recommendations in various places, such as…
- connect them directly to Vcc
- connect them directly to GND
- connect them to Vcc through a pull-up resistor
- connect them to GND through a pull-down resistor
What are the pros and cons of each of these options? Which option is best for stability and low power consumption?
Best Answer
There are a few considerations that have not been mentioned in other answers.