The input voltage are compatible with TTL output voltage. These devices may be used as a level converter for interfacing 3.3 V to 5 V system. Input protection and output circuit ensure that 0 to 5.5 V can be applied to the input and output (*) pins without regard to the supply voltage. These structure prevents device destruction due to mismatched supply and input/output voltages such as battery back up, hot board insertion, etc. *: output in off-state