The LMK1D121x family of devices is designed to support fail-safe input operation feature. This feature allows the user to drive the device inputs before V_DD is applied without damaging the device. Refer to Section 7 for more information on the maximum input supported by the device. User should note that incorporating the fail-safe inputs also results in a slight increase in clock input pin capacitance.

The device also incorporates an input hysteresis which prevents random oscillation in absence of an input signal. Furthermore, this feature allows the input pins to be left open.