A full digital temperature and voltage sensor for field testing
In this talk we present a novel digital sensor to measure temperature and voltage on a VLSI chip simultaneously. The sensor is composed of logic circuits including ring oscillators, and all computations are done with fully digital process. Compared with the conventional analog sensors, the digital sensor has several technical merits which are small chip area, quick response time, low power dissipation and no need to prepare A/D convertor and reference current/voltage.
Therefore, more than one sensor can be placed at various locations on a chip. In addition, the sensor can have an aging-tolerant structure for electro-migration, BTI and HCI. In order to reduce the influence of process variations on measurement accuracy, a calibration method that uses an initial measurement value of each sensor is adopted. In order to estimate measurement accuracy of the sensor, experimental results using circuit simulation and fabricated test chips are also presented where we investigate the effectiveness of the sensor derived from reduction of temporal and spatial variations.
The comprehensive evaluations show that the total measurement error is smaller than the analog sensors’ and it implies the importance of real time and contiguous measurement.