Reading Datasheets: Output-Tolerant Function

What is the output-tolerant function?
The output circuitry of CMOS logic ICs has a totem-pole configuration consisting of a pair of p-channel and n-channel MOSFETs as shown below. Typically, CMOS logic ICs have a parasitic diode between an output and power supply.

The parasitic diode turns on when voltage is applied to an IC when it is off or to an IC with a three-state output (such as the 74LCX245) when it is on. The IC might be destroyed by the resulting large current.
Even when a voltage higher than the supply voltage (V_CC) is applied to the output, current does not flow into an IC with an output configuration that does not have this parasitic diode. Such an IC has an output-tolerant function.

It is easy to distinguish whether an IC has an output-tolerant function.
Let’s look at the datasheets for ICs of the 74VHC and 74LCX Series.

See the bus I/O voltage shown in the Operating Ranges table.
The datasheet of the 74VHC245 shows V_IO＝０ to V_CC. This means that the output pin is tolerant of only up to V_CC. Therefore, the 74VHC245 does not have an output-tolerant function.
In contrast, the datasheet of the 74LCX245 shows V_IN＝０to 5.5 V, meaning that up to 5.5 V can be applied to the bus I/O pin regardless of V_CC. Therefore, the 74LCX245 has an output-tolerant function.