Unified Vdd Vth Optimization Based DVFM Controller for a Logic Block

In this paper analytical expressions for optimal V
_dd
and V
_th
to minimize energy for a given speed constraint are derived. These expressions are based on the EKV model for transistors and are valid in both strong inversion and sub threshold regions. The effect of gate leakage on the optimal V
_dd
and V
_th
is analyzed. A new gradient based algorithm for controlling V
_dd
and V
_th
based on delay and power monitoring results is proposed. A V
_dd
-V
_th
controller which uses the algorithm to dynamically control the supply and threshold voltage of a representative logic block (sum of absolute difference computation of an MPEG decoder) is designed. Simulation results using 65 nm predictive technology models are given.