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Bidirectional adaptive body bias (ABB) is used to compensate for die-to-die parameter variations by applying an optimum pMOS and nMOS body bias voltage to each die which maximizes the die frequency subject to a power constraint. Measurements on a 150 nm CMOS test chip which incorporates on-chip ABB, show that ABB reduces variation in die frequency by a factor of seven, while improving the die acceptance rate. An enhancement of this technique, that compensates for within-die parameter variations as well, increases the number of dies accepted in the highest frequency bin. ABB is therefore shown to provide bin split improvement in the presence of increasing process parameter variations.
Date of Publication: Nov 2002