I will use this 12V voltage regulator which in my case marked as MC7812ABT and TO−220 package. And I want to use it for a 12V 16mA load where it will regulate 24V supply to 12V. In the datasheet there is a section which confuses me:

enter image description here

There is 19V, 27V and 30V ect. mentioned. In my case the output will be 12V, can the input voltage be 24V?

  • \$\begingroup\$ Yes, you can use it Vin max = 35V \$\endgroup\$
    – G36
    Commented Apr 6, 2020 at 11:04

1 Answer 1


For maximum input, refer to the "Maximum Ratings" section. In your case, as you have a 12 V part (MC7812ABT), VI-max=35 V. enter image description here

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.

enter image description here

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


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. enter image description here

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.

enter image description here

  • \$\begingroup\$ What is 221A? And in my screenshot MC7812AB is the closest thing in the datasheet to MC7812ABT. I dont understand the method to conclude what makes the result as 35V in my case. Could you explain it more explicitly? \$\endgroup\$
    – user1245
    Commented Apr 8, 2020 at 21:41
  • \$\begingroup\$ Sure - pleae see my updated answer. Your screenshot shows the table for MC7812B, not MC7812AB, but the difference is marginal. \$\endgroup\$
    – Janos
    Commented Apr 9, 2020 at 16:23

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