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Specs - typical and maximum - what to use?

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atferrari

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How the professionals do it?

Given a certain spec (like for the LM 337):

Min I load : typical 2,5 mA - max 10 mA

Should I calculate my circuit for those 10 mA? Or hope it is 2,5 mA?

Please note that my question is not about the regulator but about how a correct design should be done.
 
The typical value is how much it probably needs, most of the time.

The max value 10mA is how much it might need in some cases, maybe for max voltage/current output and/or at temperature extremes when the silicon is less efficient.

As for "correct" that depends on your requirements I guess?
 
Typical is a 'average' and certainly not a min or max. For a hobby you use what you have. For production where you are using 1000000 parts you will see some at max and some at min and all part need to work.

At the hobby level your part may not be a average part at all but may be a reject part and be near max. You need to try it and see.
 
If your design will allow it you should always use worst case (Min. / max.) values.
In the example you noted you can almost always increase the load.
 
hi atf,

For a professional design I would use the maximum value, [worst case value] not the value measured on your LM337.

Reason for this is to ensure that if the part needs replacing in the future, the replacement can be any off the shelf LM337, not a select on test LM337.

Its possible that in the future if the part fails, you may not be the engineer who is doing the repair.

Also if you build more than one unit, using that circuit design, it would mean that every LM337 that you use would have to be selected to be the same.

E.
 
normal "safety margins" on components used to be 20% as a rule of thumb. in other words, if a transistor is rated at 250V, it would be used in a circuit where the maximum voltage across the transistor would be 200V or less. now with far east companies trying to squeeze every penny out of products, the safety margins have become smaller, often between zero and 10%. this has the immediate effect of lowering production costs, but also makes the products less reliable, resulting in a higher percentage of in-warranty failures. unfortunately, for some reason, the bean counters never factor in the warranty failures and their repair costs, but only see the increased profits on the front end as a result of lower cost, and on the back end when people just throw away the failed product and buy a new one.
 
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