In-Situ Delay Characterization and Local Supply Voltage Adjustment for Compensation of Local Parametric Variations

A method is proposed to compensate for local delay variations by adjusting the supply voltage of individual circuit blocks. In-situ characterization of sub-blocks allows for voltage adjustment with minimum safety margin. Different strategies and circuit techniques for in-situ delay characterization of sub-blocks are described and compared. A dual V_DD/power switch scheme is proposed for discrete voltage assignment to individual sub-blocks. Experimental results are presented for a test module based on an ARM9 core, fabricated in 130-nm CMOS. Yield improvement and power reduction capabilities are demonstrated by Monte Carlo simulations. For a typical setting, a reduction of 10% in power can be achieved with the proposed dual V_DD/power switch concept. Using more than two supply voltages is shown to produce only small additional power savings at the price of high area overhead. The effect of the proposed scheme increases with increasing intra-die variability, which makes it suitable especially for future technologies.