# Footprint dimensions don't add up

The screen capture below was taken from the datasheet for Pulse's PA2369NL transformer.

However, it doesn't make much sense to me. All measurements are in mm.

Take for example, the separation between the top and bottom rows of pads. According to the image, each pad has a length of 2.54mm. The inner distance between the two rows is given as 13.36mm. Now if my math is correct, that would make the outer dimension 13.36mm + 2 * 2.54mm which gives 18.44mm, not the 18.16mm given.

What am I missing here?

• Looks like the author did not care much about the math Sep 21, 2021 at 20:44
• A little extra length on the pads projecting past the transformer won't hurt and may make soldering easier. Sep 21, 2021 at 21:07
• Technically nothing says the pads in the bottom row have to have the same dimensions as the pads in the top row. Just make the pads in the top row 2.26 mm in the y direction and everything adds up fine. Sep 21, 2021 at 22:19

## 1 Answer

You are correct, the numbers do not add up. I would say you aren't missing anything.

It is not uncommon to encounter errors in datasheets. I advise you try to contact your rep and let them know, and also inquire which dimension is correct. (My company has contacted several manufacturers regarding errors we have found in datasheets; usually they acknowledge it and issue an errata within several months to a year.)

• You should also get a sample of the part to make sure the "corrected" dimensions match reality.
– qrk
Sep 21, 2021 at 22:11