High-Precision Mixed-Signal Sensor Interface for a Wide Temperature Range [0–300°C]

Abstract

Sensor interfacing is a crucial component for today's systems in many application domains. Especially in automotive and manufacturing fields, high temperatures are encountered. For extracting the typically small sensor signals, an interface near the sensor is needed to provide high accuracy and robustness. This results in challenges in circuit design and architecture to avoid temperature-related nonideal effects. In this contribution, we present a novel system architecture for a Wheatstone bridge interfacing system. By encoding the sensor signal in time domain and augmenting the system with additional observations, we present a robust and precise sensor interface operating at up to 300°C without breaking accuracy or functional requirements because of high-temperature effects. We present a realization of this concept proven to be accurate within ±1.3% full scale over the full temperature range.

A Temperature-Hardened Sensor Interface with a 12-Bit Digital Output Using a Novel Pulse Width Modulation Technique

“…Considering the constraint of thermally stable performance, time-domain sensor interfaces have appeared that are more competitive than classical analog sensor interfaces [ 6 , 7 , 8 , 9 ]. The time-domain approach is based on converting the sensor analog output into a time domain signal; a frequency, or a phase shift (for example a pulse width of pulse width modulated (PWM) signal), which can be easily digitized with the use of a time to digital converter (TDC) [ 10 , 11 ].…”

“…A 79 ppm/°C thermal drift of the sensor interface has been measured. Glaser et al in [ 7 ], amplified the sensor output voltage by means of an analog amplifier before converting it into a PWM signal. Besides, a switching scheme is used to realize different measurements such as offset and temperature of the die.…”

“…It is based on the use of two injection locked relaxation oscillators to convert the transducer analog output into a PWM signal whose pulse width is defined by the difference of phase between both oscillators. Contrary to previous published works, where the PWM signal is transmitted into an ambient temperature environment for performing the signal processing [ 7 ], the signal processing of the obtained PWM signal is performed in situ, in the high temperature environment, by means of a TDC. The main feature of the presented architecture is its robustness to the thermal variations of its constitutive blocks.…”