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/sub DD/ and threshold voltage V/sub TH/ dynamic control in active and standby modes. In the active mode, on the basis of delay monitoring results, either V/sub DD/ control or V/sub TH/ control is selected to avoid any oscillation problem between them. Switching current I/sub SW/ and leakage current I/sub LEAK/ are monitored, and V/sub 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/sub DD/ and gate-oxide leakage current. Experimental results with a 90-nm CMOS device indicate that the proposed scheme results in successful I/sub SW//I/sub LEAK/ ratio maintenance and successful detection of optimum body bias conditions (I/sub OFF/ = I/sub SUB/ (= GIDL + I/sub GB/)) to within 20% of actual minimum leakage current values.