Wide-supply-range all-digital leakage variation sensor for on-chip process and temperature monitoring

Variation in process, voltage and temperature is a major obstacle in achieving energy-efficient operation of LSI. This paper proposes an all-digital on-chip circuit to monitor leakage current variations of both of the nMOSFET and pMOSFET independently. As leakage current is highly sensitive to threshold voltage and temperature, the circuit is suitable for tracking process and temperature. The circuit uses reconfigurable inhomogeneity to obtain statistical properties from a single monitor instance. An estimation method of threshold voltage variation is then developed. Cell-base design approach is taken so that design cost is minimized. Measurement results from a 65-nm test chip show the validity of the proposed circuit. Total area is 4500 μm² and active power consumption is 50 nW at 1.0 V operation. The proposed technique enables area-efficient and low-cost implementation thus can be used in product chips for applications such as testing and post-silicon tuning.