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If a sufficiently-wide range of variables were to be tested, a normal shmoo plot would show an 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, in particular a [[race condition]]. As such, a shmoo plot can be a useful test setup verification tool.
A limitation of the technique is that the extended duration of testing of the device may cause additional internal device heating, resulting in a skewing of the data (later tested cells on the plot may perform worse than earlier ones). One way of avoiding this is to exercise the device thoroughly in a similar manner immediately before the actual shmoo test.
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