Lookup Table-Based Adaptive Body Biasing of Multiple Macros

Byunghee Choi and Youngsoo Shin


A reduced supply voltage must be accompanied by a reduced threshold voltage, which makes this approach to power saving susceptible to process variation in transistor parameters, as well as resulting in increased subthreshold leakage. We propose a new adaptive body biasing scheme, based on a lookup table for independent control of multiple functional blocks on a chip, which controls leakage and also compensates for process variation at the block level. An adaptive body bias is applied to blocks in active mode and a large reverse body bias is applied to blocks in standby mode. This is achieved by a central body bias controller, which has a low overhead in terms of area, delay, and power consumption. The problem of optimizing the required set of bias voltages is formulated and solved. A design methodology for semicustom design using standard-cell elements is developed and verified with benchmark circuits.