Marc Pastre

A Hall Sensor Analog Front End for Current Measurement With Continuous Gain Calibration

This paper presents a new technique for continuously calibrating the sensitivity of a current measurement microsystem based on a Hall magnetic field sensor. An integrated reference coil generates a magnetic field for calibration. Using a variant of the chopper modulation, the spinning current technique, combined with a second modulation of the reference signal, the sensitivity of the complete system is continuously measured without interrupting normal operation. Modulation and demodulation schemes allowing the joint processing of both external and reference magnetic fields are proposed. Additional techniques for extracting the very low reference signal are presented. The implementation of the microsystem is then discussed. Finally, measurements validate the calibration principle. A thermal drift lower than 50 ppm/degC is achieved. This is 6-10 times less than in state-of-the-art implementations. Furthermore, the calibration technique also compensates drifts due to mechanical stresses and ageing

Global Modeling Strategy of Parasitic Coupled Currents Induced by Minority-Carrier Propagation in Semiconductor Substrates

This paper presents a modeling strategy to simulate the propagation of electrical perturbations induced by direct biasing of substrate junctions. Usually, this is done by identifying parasitic substrate devices such as bipolar transistors. However, mapping a topology with these bipolar transistors rapidly reaches its limits when several junctions are acting at the same time. In this paper, we propose a new modeling methodology of parasitic signals. It relies on a generalized model of p-n junctions and resistances that takes into account minority-carrier densities and gradients at the boundaries. We show that bipolar-transistor- and thyristor-related effects can be obtained from a network interconnection of these extended devices. Furthermore, we show that this modeling approach could be easily extended to simulate complex 3-D layouts.

A Hall sensor analog front end for current measurement with continuous gain calibration

This paper presents a new technique for continuously calibrating the sensitivity of a current measurement microsystem based on a Hall magnetic field sensor. An integrated reference coil generates a magnetic field for calibration. Using a variant of the chopper modulation, the spinning current technique, combined with a second modulation of the reference signal, the sensitivity of the complete system is continuously measured without interrupting normal operation. Modulation and demodulation schemes allowing the joint processing of both external and reference magnetic fields are proposed. Additional techniques for extracting the very low reference signal are presented. The implementation of the microsystem is then discussed. Finally, measurements validate the calibration principle. A thermal drift lower than 50 ppm/degC is achieved. This is 6-10 times less than in state-of-the-art implementations. Furthermore, the calibration technique also compensates drifts due to mechanical stresses and ageing

Automatic calibration of Hall sensor microsystems

In many applications, a Hall element is used for contact-less measurement such as linear and angular positions, electrical current, power and energy, etc. The Hall element fabricated by means of CMOS technology features mediocre characteristics [R.S. Popovic, Z. Randjelovic, D. Manic, Integrated Hall-Effect Magnetic Sensors, EMSA, Germany, 2000; R.S. Popovic, Hall Effect Devices, Adam Hilger, Bristol, Philadelphia, New York, 1991]. It gives a weak output signal of the order of a few mV. This signal is often corrupted by sensor offset, noise, temperature and aging drift. This paper deals with the state of the art and main techniques capable to detect and compensate these issues. Case studies using mentioned techniques are also summarized.

A hall sensor-based current measurement microsystem with continuous gain calibration

A novel technique for the continuous calibration of the sensitivity of Hall sensors is presented. Using an integrated coil and a new modulation/demodulation scheme, the sensitivity is measured and its drift eliminated. The obtained thermal drift is 50 ppm/degrees C, which corresponds to a reduction by a factor of 6-10 compared to the previous state of the art. The sensitivity drift due to purely mechanical stresses and ageing is also cancelled.

High-Speed Power System Transient Stability Simulation Using Highly Dedicated Hardware

This paper presents a fully analog demonstrator based on power system emulation for high-speed power system stability analysis. A benchmark using a fixed two-machine topology has been implemented. The characteristics of the emulated components (i.e., generators and transmission lines) are reprogrammable and short circuits can be emulated at different distances from the generator. This first realization is limited to transient stability analysis, as the main focus during design was put on computation speed. Indeed, the emulated phenomena are 10 000 times faster than real time. Moreover the authors aim to emphasize that such highly dedicated computation architectures are not only competitive in terms of speed, but also in terms of modularity.

Navigation grade MEMS accelerometer

This paper reports on a high performance navigation grade MEMS servo accelerometer targeted at inertial applications. Reported results are for a bulk MEMS capacitive sensor with 11g full scale over a 300 Hz bandwidth interfaced with a highly optimized servo-loop 5^th-order sigma-delta electronic. Measurements demonstrate a long-term bias stability of +/−0.2mg, a second order non-linearity K2 ≪5 µg/g², an in-band noise floor of 1 µg/√Hz and a Dynamic Range over 1 Hz bandwidth of 22 bits.

A fully integrated Hall sensor microsystem for contactless current measurement

Contactless current measurement based on Hall-effect sensors can be performed in either closed- or open- loop configuration. In this paper an open-loop sensor system with a current-mode output is described. The system measures the magnetic field induced around the current path targeting high linearity, accuracy and speed. As the accuracy of the Hall sensor microsystem is affected by temperature-dependent offset and sensitivity of the sensing element, system-level solutions are developed to minimize these effects. The full system integration represents a design challenge as both voltage and current references are directly involved in the sensitivity calibration and both contribute to the system sensitivity drift. The measurements show a sensitivity drift lower than 80ppm/°C, the offset drifts less than 300nT/°C and the non-linearity is less than ±0.08%. The effects of the varying external field on the calibration loop are analyzed and the theoretical prediction is validated by measurement.

A 300Hz 19b DR capacitive accelerometer based on a versatile front end in a 5 th -order ΔΣ loop

This paper presents a 5^th-order ΔΣ capacitive accelerometer. The ΔΣ loop is implemented in mixed signal, the global 5^th-order filter having a 2^nd-order analog and a 3^rd-order digital part. The system can be used with a wide range of sensors, because the mixed-signal front end is programmable. The ASIC developed comprises a voltage-mode preamplifier, two parallel demodulators implementing CDS, and a 7-bit Flash ADC. The latter drives a 3^rd-order digital filter, which can be configured for different sensor parameters in order to ensure overall loop stability and optimize the noise performance. With a low-noise MEMS sensor, the system achieves a 19-bit DR and a 16-bit SNR, both over a 300Hz bandwidth.

SOI capacitor-less 1-transistor DRAM sensing scheme with automatic reference generation

Recently, the new concept of the capacitor-less 1T DRAM cell has been developed. The memory cell (MC) using a single transistor on SOI exploits the Floating Body (FB) effect of partially depleted (PD) SOI devices. The memory state can be read through the drain current of the storage transistors, i.e. I/sub 0/ and I/sub 1/ respectively. To read the information stored in a 1T DRAM cell, the current of the selected MC is compared to I/sub ref/ . In this paper, we propose a sensing method with automatic reference generation for SOI capacitor-less 1T DRAM. An adjustable current source is implemented as reference current source in order to sense the MC state. A digital-to-analog converter (DAC) and a successive approximation algorithm perform the calibration of I/sub ref/.