# What is the relevance of “typical values” in datasheets?

When working on a design I always work with minimum/maximum values from the datasheet (whichever is worst case), never typical values. I was reminded when in another discussion the leakage current for a BAS416 diode came up: 3pA typical, 5nA maximum. That's a factor 1000! In this case I surely would dismiss the 3pA.
What's the relevance of "typical values" in general? Do you use them in a design?

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One thing to bear in mind when reading technical datasheets, is they are finalised by marketeers!!! not engineers. If it was up to engineers to publish datasheets you would only have the min/max relevant values and more information about the statiscal variations that you can expect.

Many people are involved with the writing of the datasheets, and ultimately it is people in marketing that have the final say!

So when you read a typical value that is so far away from the min/max values that is simply marketers doing there thing. Generally when doing a parametric search typical values are what are listed and get you in to review the datasheet. Latter on you discover that 3pA is a maximum of 5 nA, sometimes latter in the design process!!

I will generally review the min/max values to really appreciate the range and perform worst case calculations/montecarlo analysis to really work out the expected performance!

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Often, the only useful information on the first page is the part number - The rest is marketing mumbo-jumbo. –  Kevin Vermeer Dec 5 '10 at 19:51

When estimating battery life in a device, I tend to use the typical values. If you use maximum values, you'd end up with a much shorter battery lifetime than would "typically" be achieved. Usually it is the typical battery life that one would be interested in, and not some extremely short time that will never result anyway.

Sure, when you're designing power supplies..etc, I would take max current consumption values for all the devices that it's going to power as a safeguard.

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@cksa361: "...will never result anyway". I don't agree here. Since they're mentioned as maximum values it means they may occur, you just don't know how often. Maybe some statistic like standard deviation (typical value should be the mean) would help. –  stevenvh Dec 3 '10 at 9:14
@cksa361: re battery life. Suppose you design a handheld device which according to typical values would work for 10 hours on a single battery charge. If the current may be 100 times as large (not even the 1000 like in the BAS416) on some devices the battery will be drained in 6 minutes. Is the device defective? No, you say, it was designed according to the given specs. Yes, I say, your product looses credibility and you'll have to give the customer another one. Which may also be defective. How about 10% of your production?.... –  stevenvh Dec 3 '10 at 10:00
but then if you start working with maximum's it's not useful. Go design a product with a 10 hour battery life based on maximum current ratings. You'd end up compromising on increased price, increased battery size and weight, and a battery life that is typically far more in excess than what the user needs. –  cksa361 Dec 3 '10 at 10:05
i think being a perfectionist and overengineering products is counter productive. Take into account typical values because it is what would typically happen (i.e. most of the time). –  cksa361 Dec 3 '10 at 10:09
@cksa361: "most of the time". Exactly, like in 90% of the time. Which means 10% rejects, which is unacceptable in any production IMO. Let's see what others have to say about this. –  stevenvh Dec 3 '10 at 10:28
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You may optimize for the typical case. For example if I need 5 A max but 2 A typical, I will design/buy a 5 A supply but choose the one that is most efficient at 2 A.

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Often when companies spec those values they have not done that much work determining it. I have talked to many companies that their specs are purely off of simulation of what variances they will have in production.

If you are making a million phones, check the spec on what you are buying, determine what is feasible. if you have to trash 1 phone out of 1/1000 because you get a perfect storm of devices being out of spec, that is probably much better than manufacturing problems. If the diode is almost always worst case, get a different diode.

If you are making 3, fab them for typical, allowing some tolerance, and if it ends up having a major variance in one part, replace it with another. If it is mission critical part, check it first.

If over-spec is not an issue for your 3, just spec worst case. You will spend more on components then you need, but you are building three, 10 dollars only makes 30. No real cost lost. If you are making millions, you need to confirm conformance yourself.

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Someone downvoted me. I could see many reasons someone would disagree with me, although I would like to know which one they chose. –  Kortuk Dec 4 '10 at 23:34