I am a novice trying to build a circuit using a L4904v5 voltage regulator. The datasheet has the following images: Flat drawing showing pinout of L4940v5 TO-220 package 3D drawing of L4940v5 TO-220 Actual image OF L4940v5 TO-220

This 2D pinout drawing gives me few clues about which side I am viewing it from. I assume it was viewed from the side is "flat" and does not have the "side dimples" or the round hole since they are not shown in the pinout image. There is also a lightly printed symbol on one of the pins that you can see in the actual picture. I do not recognize the symbol though.

1) Is my interpretation correct? 2) If I am wrong, will connecting this regulator backwards, to a 7.5 volt source, damage it? 3) What does the symbol mean?


1 Answer 1


It would be obvious if you had the physical component in hand. If the drawing was viewed from the side of the heatsink tab (i.e. the rear) it would look completely different. Assume connecting anything that is polarized in reverse will damage it.

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Wholly appropriate images taken from Interface Bus

  • \$\begingroup\$ I actually do have the part. The drawing does not seem to accurately reflect either side. If it is the front, it is missing the round hole and side dimples. If it is the back, it should not have the horizontal lines in the middle since it is flat on that side. I think you are telling me however, that this drawing is showing the front. \$\endgroup\$
    – Moby Disk
    May 1, 2020 at 19:00
  • 1
    \$\begingroup\$ @MobyDisk Yes, that is what I am telling you. The reason this is the front is because you can see the chamfered edge where the plastic meets the metal. Don't expect approximate line drawings to contain every detail on the package (the dimples being one of those). Different TO-220 packages may or may not have dimples but they are all TO-220. \$\endgroup\$
    – DKNguyen
    May 1, 2020 at 19:20

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