Electronic – Whence this difference in supply current


When I need a MAX809 I prefer the OnSemi part over those from Maxim or NXP because the former has a much lower supply current. But I was looking at the NXP datasheet again recently, and I noticed that there's a big difference in supply current depending on package:

Typical: 24\$\mu\$A
Maximum: 60\$\mu\$A
Typical: 24\$\mu\$A
Maximum: 35\$\mu\$A

Compare with the OnSemi (both packages)
Typical: 0.8\$\mu\$A
Maximum: 1.8\$\mu\$A

So for the SOT-23 that's nearly double the SC-70's value. I realize that a SOT-23 can dissipate a bit more power than an SC-70, but these values are under the same temperature conditions. The Maxim datasheet gives exactly the same figures, while OnSemi doesn't differentiate between packages.
How can this difference be explained?

Best Answer

This difference could be explained in a number of ways, though none definitive without knowing more about the device than the datasheet (necessarily) reveals. These may include differences between the actual structures of the underlying devices within the packaging (most likely), as well as differences in the estimations, testing practices, and / or acceptable margins of the companies or even specific engineers involved in their design and documentation. It is conceivable that typos in the actual datasheets themselves could be blamed. Nothing is certain until it can be proven that it works, and even then, things (manufacturing processes, etc) can change over time without you (or even the distributor, documentarian) necessarily being informed. Good testing procedures, performed on all devices prior to distribution (i.e. quality control) and wide operational margins for parts selection can help to insulate you from problems inherent in both mis-specification and changes in manufacturing over time, but don't be surprised if your (initial) design requires re-work somewhere along the line because of these things.

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