Electronic – Interpolating output specs on SN74LVC1T45 transceiver

(edit: misunderstood a sentence in the question; I thought that you had connected Vref to the Vdd pin. I added a picture of the pinout to the question.)

Yes, it's confusing when it means that the maximum is minimum xxx :-)

"As long as the voltage is below 0.3Vdd, the MCP3202 will regard it as a digital zero"

That's the right interpretation.

But it's not a good idea to use the same voltage for power and ADC reference. Your power supply voltage isn't clean enough. Power should be a bit higher (what's wrong with 5 V?), and you use a voltage reference for the ADC reference voltage (maybe that's what the 4.096 V is?), or you use an RC filter to derive the reference from the 5 V if the absolute accuracy isn't important.

The problem is not in the maximum low, and minimum high levels, but in the maximum high. The PIC will output 5 V, which is a volt higher than the ADC's supply. Absolute maximum ratings, on page 2 of the datasheet say that no voltage should exceed Vcc by more than 0.6 V. Absolute Maximum Ratings. Read below the table:

*Notice: Stresses above those listed under “Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability.

(my emphasis)

So, if you would use for instance the MCP1541 as a reference you can use a 5 V supply for that, and the ADC.

On page 38 of the datasheet you'll see for instance that the voltage on the PB should never exceed Vcc + 0.3 V. You'll find that this is true for almost all inputs on ICs: the input levels should remain between the rails. An exception is when you have for instance 5 V tolerant inputs on a 3.3 V powered microcontroller, but then that will be clearly indicated in the datasheet. (The manufacturer will consider this as an important feature, so he will make sure you notice that.)

To know if the high output will damage the input of another IC with a Vcc of 2.7 V you'll have to consult the datasheet of that IC. Probably the same limits will apply: input voltage should be no higher than the 2.7 V supply.