# Multiple lengths in DAC datasheet

The last page of this DAC datasheet gives dimensions of the chip:

Some of these dimensions come is 3-tuples (such as the pin width: 0.30 | 0.37 | 0.45). What does each of the numbers mean? Is it min, mean and max?

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## 1 Answer

The second is nominal, not mean. But yes, height is 0.95 mm minimum, 1.00 mm nominal, and 1.05 mm maximum.

The difference between mean and nominal is that nominal is the target dimension, that's the aim. Mean usually means arithmetic mean, but that may deviate from nominal, depending on spread.

This could be a statistic on the package thickness. Apparently the injection mold wasn't made precise enough, so that the mean thickness is 1.01 mm (purple line). But the nominal thickness is still 1.00, with 0.95 mm and 1.05 mm as limits. So even with a mean deviating from nominal that condition is met.

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Nominal? Is there a strict definition in electronics? Wikipedia's definition is a bit wishy-washy. –  Randomblue Aug 11 '12 at 12:47
Already added! :-) –  stevenvh Aug 11 '12 at 12:48
I would expect (tell me if you agree) that if manufacturing processes improve such that later parts have finer tolerances, the nominal dimension would generally be expected to be within, or at and end of, the new tolerance range. For example, it would be considered quirky for a manufacturer to offer revised specifications for the above-described part with a minimum dimension of 1.009mm and a maximum of 1.011mm, though it might revise the specs to e.g. 0.990mm and 1.00000mm. –  supercat May 14 at 20:33
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