A dynamic voltage scaling circuit design based on critical path replica and time warning techniques

Abstract

Critical path replica (CPR) is a widely used technique in synchronous digital circuit design. However, the existing CPR technique cannot accurately reflect the timing of the circuit due to local process variations (LPV). An improved CPR technique based on load capacitance matching (LCM) is proposed in this paper, which can track critical path delay across wide voltage range. The impact of LPV is simulated under wide voltage range, and a configurable delay line is designed to eliminate the effect of LPV. Furthermore, a low overhead mixed-threshold transition detector (TD) circuit is also proposed to monitor timing violations of the replica path, which generate an ‘error’ signal used to dynamically regulate the chip’s operating voltage. The proposed techniques are implemented on a CORDIC chip using the 55-nm CMOS process. Simulation results show that in the near-threshold voltage (NTV) region, the supply voltage can be reduced from 0.8 to 0.6 V, enabling a maximum of 42.6% power saving at the TT corner, 25°C with lesser than 1% area overhead as compared to the baseline design.