Self calibrating circuit design for variation tolerant VLSI systems

Increasing leakage current and aggravating process variations are showing impact on dynamic circuit performance and robustness as technology scales into the nanometer regime. This paper describes a self-calibrating process compensating dynamic (PCD) circuit technique for maintaining the performance benefit of dynamic circuits and reducing the variation in delay and robustness. A variable strength keeper that is optimally programmed based on the die leakage enables 10% faster performance, 35% reduction in delay variation, and 5× reduction in the number of robustness failing dies compared to conventional designs. A new leakage current sensor design is also presented that can detect leakage variation and generate the keeper control signals for the PCD technique. The proposed 6-channel leakage current sensor enables high-resolution on-chip leakage measurements from multiple locations of a die, saving testing cost and realizing both die-to-die and within-die process compensation. Results based on measured leakage data show 1.9-10.2× higher signal-to-noise ratio and reduced sensitivity to supply and P/N skew variations compared to prior leakage sensor designs. The PCD technique with the on-die leakage current sensor is applied to a 2-read, 2-write ported 128 × 32b register file and a test chip is fabricated in 1.2V, 90nm dual-V, CMOS process.