A field programmable gate array-based digital temperature sensor's response to supply voltage variation

Digital temperature sensing sometimes suffer inaccuracy as a result of Vdd variation generating noise within a digital temperature sensor, built around ring oscillators. Thus, noise generated affects ring oscillator's frequency. In this paper, a delay-based digital temperature sensor is formulated, implemented and evaluated on a Field Programmable Gate Array Chip. The temperature sensor is realized using Very High-Speed Integrated Circuit Hardware Description Language and synthesized in Quartus II. The realized digital circuit was implemented on an Altera DE3 board with a Stratix III Field Programmable Gate Array chip. Data obtained was analysed using Least-Square interpolation method to determine the effect of voltage drop. The result is a resource efficient digital temperature sensor sensitive to variation in Vdd less than 3.3V. A measurement error of -2.3°C ~ +2.1°C was obtained at Vdd of 3.3V and -2.7°C ~ +1.7°C when Vdd equal 1.5V for a temperature range within 40°C ~ 120°C.