Hey guys, i have some questions about teh considerations when making a package in eagle. I'm working on the TPS2490.
First: the datasheet shows the dimension tolerances for this part in a max/min format, for instance: width of the chip without pins is shown as 3.1/2.9, and width with pins is 5.05/4.75. Tim, I believe in the tutorial, you managed this issue for the chip width (w/o pins) by simply making the line with which you drew the footprint have a width = to the tolerance. Thus, for this chip I would make the line 0.1 mm wide to compensate for the +/- 0.2mm overall tolerance. My question is how do we handle the situation with pin length tolerance? At this point, to calculate pin length I did the following: ((Min. width w/ pins) - (max width w/o pins))/2 = 0.825mm As i think about it though, I'm not sure this is the right thing to do as I am unsure as to what would should constitute the worst case scenario as far as dimensions are concerned. Also, once the appropriate pin length is calculated, where should it be placed with respect to chip width? in other words, should the edge of each pin be placed at the min (2.9mm/2) from center, the median (3mm/2) from center, or max (3.1mm/2) from center? Second: the datasheet also includes dimensions for gauge plane and seating plane. Do these need to be taken into account, and if so, how do I do that in eagle? Thanks guys! Scott
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