Shmoo plot: Difference between revisions

Revision as of 18:46, 20 February 2012

Revision as of 20:49, 14 May 2012

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[[File:64K DRAM Shmoo Plot-typical.png|thumb|left|Normal shmoo plot]]

[[File:64K DRAM Shmoo Plot-abnormal.png|thumb|right|Abnormal shmoo plot]]

If a sufficiently-wide range of variables were to be tested, a normal shmoo plot would show nan operating envelope of some shape not unlike Al Capp's [[Shmoo]], but in practice, this might damage the [[device under test]], and finer-grained views are of much more interest, particularly focusing on published component margins (e.g., - 5% Vcc). When this is done, the operating envelope typically extends to the border of the plot in one or more directions.

Sometimes a shmoo plot has an unusual and surprising shape, and while it is difficult to determine the exact cause, it is sometimes due to some unusual defect (perhaps in only part of a circuit) coupled with otherwise normal operation. In other cases, it might be an artifact of the electrical testing setup or the test program used. As such, a shmoo plot can be a useful test setup verification tool.