Fail-safe logic circuitry allows voltages on the logic control pins to be applied before the supply pins, protecting the device from potential damage. Additionally the fail safe logic feature allows the logic inputs of the mux to be interfaced with high voltages, allowing for simplified interfacing if only high voltage control signals are present. The logic inputs are protected against positive faults of up to +48 V in powered-off condition, but do not offer protection against negative over-voltage condition.

Fail-safe logic also allows the devices to interface with a voltage greater than V_DD on the control pins during normal operation to add maximum flexibility in system design. For example, with a V_DD = 15 V, the logic control pins could be connected to +24 V for a logic high signal which allows different types of signals, such as analog feedback voltages, to be used when controlling the logic inputs. Regardless of the supply voltage, the logic inputs can be interfaced as high as 48 V.