A CMOS Readout Circuit for Resistive Transducers Based on Algorithmic Resistance and Power Measurement

A CMOS Readout Circuit for Resistive Transducers Based on Algorithmic Resistance and Power Measurement

Cai, Z. (TU Delft Electronic Instrumentation)
Rueda Guerrero, Luis E. (Industrial University of Santander)
Louwerse, Alexander Mattheus Robert (External organisation)
Suy, Hilco (BL Environmental Sensors)
van Veldhoven, Robert (NXP Semiconductors)
Makinwa, K.A.A. (TU Delft Microelectronics)
Pertijs, M.A.P. (TU Delft Electronic Instrumentation)

Microelectronics

2017

This paper reports a readout circuit capable of accurately measuring not only the resistance of a resistive transducer, but also the power dissipated in it, which is a critical parameter in thermal flow sensors or thermal-conductivity sensors. A front-end circuit, integrated in a standard CMOS technology, sets the voltage drop across the transducer, and senses the resulting current via an on-chip reference resistor. The voltages across the transducer and the reference resistor are digitized by a time-multiplexed high-resolution analog-todigital converter (ADC) and post-processed to calculate resistance and power dissipation. To obtain accurate resistance and power readings, a voltage reference and a temperature-compensated reference resistor are required. An accurate voltage reference is constructed algorithmically, without relying on precision analog signal processing, by using the ADC to successively digitize the base-emitter voltages of an on-chip bipolar transistor biased at several different current levels, and then combining the results to obtain the equivalent of a precision curvature-corrected bandgap reference with a temperature coefficient of 18 ppm/°C, which is close to the state-of-the-art. We show that the same ADC readings can be used to determine die temperature, with an absolute inaccuracy of ±0.25 °C (5 samples, min-max) after a 1-point trim. This information is used to compensate for the temperature dependence of the on-chip polysilicon reference resistor, effectively providing a temperature-compensated resistance reference. With this approach, the resistance and power dissipation of a 100 Ω transducer have been measured with an inaccuracy of less than ±0.55 Ω and ±0.8%, respectively, from -40 °C to 125 °C.

http://resolver.tudelft.nl/uuid:3d665226-0e79-4a0e-91d6-f3e7c0baaf3e

https://doi.org/10.1109/jsen.2017.2764161

1530-437X

IEEE Sensors Journal, 17 (23), 7917-7927

Accepted Author Manuscript

Institutional Repository

journal article

© 2017 Z. Cai, Luis E. Rueda Guerrero, Alexander Mattheus Robert Louwerse, Hilco Suy, Robert van Veldhoven, K.A.A. Makinwa, M.A.P. Pertijs