Speaker
Mr
Jorge Marin
(KU Leuven)
Description
The harsh environment of space mission applications is at the same time a growing field and a challenging playground for electronic sensor systems. The need of accurate and reliable information about several parameters such as structure sanity, turbine combustion and fuel tank state, among many others, requires sensor systems to be placed *in situ*. Thus, robust, reliable and accurate sensing systems are required to operate in hostile environments under extreme temperature, pressure, humidity, vibration and radiation conditions.
Several harsh-environment-compatible features have already been demonstrated using the BBPLL-based CMOS sensor interface architecture for both capacitive and resistive sensors. The main property of this time-based architecture is the robustness provided by the direct sensor-to-digital conversion, by means of the time-domain representation of the sensor data. Since the signal does not need to be amplified before digitization, area- and power-consuming analog blocks and their nonideal effects are bypassed. Additionally, its oversampling operation provides enough redundancy to filter out in the digital domain corrupted data produced by analog transient effects such as single-event radiation effects. Another feature is the highly-digital implementation, compatible with digitally-assisted techniques such as time-based signal chopping and differential-path tuning which can improve the resolution and accuracy performance of the system by reducing the effect of DC and low-frequency perturbations. These techniques can be configured to implement simple built-in self-test strategies that can provide information about the state of the circuit and feed it back for compensation. In such way, smart system-level operation can be achieved by driving capabilities at local level, for example in the case of wireless sensor networks.
This paper presents an overview of the robustness properties of time-based sensor interfaces demonstrated until now in CMOS technologies, which indicate a good compatibility with space applications. Furthermore, the presented demonstrators constitute a good example on how CMOS technologies are used as a low-cost prototyping platform to explore space solutions to be further implemented in more expensive technologies used in space applications.
Two study cases are discussed. The first demonstrator is a BBPLL-based capacitive sensor interface which can achieve 14-bit resolution. The interface uses time-domain chopping as the main source of compensation between the VCOs mismatch and low-frequency noise. It shows high linearity operation, which simplifies calibration by reducing the number of calibration data points needed.
The second interface is a fully-differential BBPLL-based resistive-bridge sensor interface. It provides a very high drift resilience by combining different digitally-assisted techniques. A simple online monitoring technique allows to compensate for sources of drift other than temperature, such as package strain variations and circuit component degradation. Thus, this interface is suited for very harsh environments. The target temperatures in this work, even if far from the maximum required values for space applications, demonstrate the validity of the subjacent principles.
The examples discussed have medium-to-high resolution, consume low power and a have a small footprint. This implies low-weight implementations since low volumes are needed for the chip and the batteries. This work constitutes a step towards robust, accurate, light/compact and smart wireless sensor systems which can collect and process high fidelity data locally in nowadays’ space missions.
Primary author
Mr
Jorge Marin
(KU Leuven)
Co-authors
Mrs
Elisa Sacco
(KU Leuven)
Prof.
Georges Gielen
(KU Leuven)
