LBIST and weighted LBIST tests are performed simultaneously on different
portions of the tested object. This new test methodology and design change
achieves the same test coverage and test time as the traditional test
strategy with dramatic power reduction during test. It can be applied at
wafer, chip, MCM, and system levels of test. Most importantly, it does not
need new tools for support. Current test software will work as it does
with the traditional test strategy. Scheduling the LBIST and weighted
LBIST tests in the same test session reduces the overall power consumption
because weighted LBIST testing consumes much less power than flat LBIST
testing. In the same test session, if some parts of the logic is tested
using weighted LBIST while the others were tested using LBIST, the power
consumed by the circuit element at any given time is reduced.
