Confusion with figuring out voltage regulator maximum input voltage
For maximum input, refer to the "Maximum Ratings" section. In your case, as you have a 12 V part (MC7812ABT), VI-max=35 V.


The electrical characteristics table specifies behaviour under certain conditions. In this case, the Output Voltage is specified to be in the range 12 V (+-0.5 V) for VI = [14.8..27] V. It does not specify the output for e.g. VI=VI-max and you'd have to measure that yourself.



Note that your screenshot refers to another part, not MC7812ABT as you said you are using.

Update:

Your part is a 12 V part, which can be found in the table of all parts (ordering information). This is why you look at the "5.0 - 18 V" maximum rating, not the "24 V" one. Which tells you 35 V is the maximum.


The 221A is your case code. Here, I'm a bit lost too why they call it 221AB sometimes and sometimes 221A. Luckily in this case though, there is no difference between the cases, regarding the max input voltage.