9.2.1.2 Input Considerations

Unused inputs must be terminated to either V_CC or ground. These can be directly terminated if the input is completely unused, or they can be connected with a pull-up or pull-down resistor if the input is to be used sometimes, but not always. A pull-up resistor is used for a default state of HIGH, and a pull-down resistor is used for a default state of LOW. The resistor size is limited by drive current of the controller, leakage current into the SN74HC125-Q1, as specified in the Electrical Characteristics, and the desired input transition rate. A 10-kΩ resistor value is often used due to these factors.

The SN74HC125-Q1 has standard CMOS inputs, so input signal edge rates cannot be slow. Slow input edge rates can cause oscillations and damaging shoot-through current. The recommended rates are defined in the Recommended Operating Conditions.

Refer to the Feature Description for additional information regarding the inputs for this device.