Monitoring scheme for minimizing power consumption by means of supply and threshold voltage control in active and standby modes

This paper describes a newly developed monitoring scheme for minimizing power consumption by means of supply voltage V_DD and threshold voltage V_TH dynamic control in active and standby modes. In the active mode, on the basis of delay monitoring results, either V_DD control or V_TH control is selected to avoid any oscillation problem between them. Switching current I_SW and leakage current I_LEAK are monitored, and V_TH is adjusted so as to maintain that ratio known to indicate minimum power consumption. In the standby mode, the precision of optimum body bias monitoring is improved by taking into consideration the effects of lowered V_DD and gate-oxide leakage current. Experimental results with a 90-nm CMOS device indicate that the proposed scheme results in successful I_SW/I_LEAK ratio maintenance and successful detection of optimum body bias conditions (I_OFF = I_SUB (= GIDL + I_GB)) to within 20% of actual minimum leakage current values.