4.5
Norm-two
Figure 4.6: Optimization curves for various measurement errors.
4.5 Path selection
The accuracy of variation estimation is a function of the paths that are used for
constructing optimization problems. First of all, paths should be sensitizable; i.e.,
they should be possible to measure delay of the paths by externally stimulating
the primary input of the IC. Moreover, the paths should be linearly independent.
Ignoring the measurement noise, dependent paths provide redundant information
about the variations.
4.5.1 Sensitizable paths
As we mentioned in Section 4.1, it might not be possible to find the delay of
every arbitrary path. Only delays of the sensitizable paths (testable paths) can
be measured by externally stimulating the IC.
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