A Hybrid Multi-Path CMOS Magnetic Sensor With 76 ppm/°C Sensitivity Drift and Discrete-Time Ripple Reduction Loops

Abstract

This paper presents a temperature-insensitive magnetic sensor system for contactless current measurements. To simultaneously achieve wide bandwidth and low noise, the proposed system employs a multi-path structure with a set of spinning current Hall sensors in its low frequency (LF) path and a set of pickup coils in its high frequency (HF) path. The Hall sensors and pickup coils are used in a differential sensing arrangement that naturally rejects common-mode magnetic field interference, e.g. due to the earth's magnetic field. A common-mode AC reference field can then be used to continuously stabilize the sensitivity of the Hall sensors, which, unlike that of the pickup coils, is quite temperature dependent. In this design, the ripple reduction loops in the Hall sensor readout are implemented in a discrete-time manner, and so occupy 20% less area than a previous continuous-time implementation. Over a-45˚C to 105˚C temperature range, the proposed system reduces Hall sensor drift from 22% to 1%, which corresponds to a temperature coefficient of 76 ppm/˚C. I.

Amplitude modulated feed-forward thermal drift compensation for linear and nonlinear current sensors

“…The type 3 thermal sensor in the interdigitated capacitive thermal sensor is prepared in the laboratory following the procedure explained below. At the beginning of the process, 40 g standard zinc oxide (ZnO) powder was added with 3 N Sulphuric acid (H 2 SO 4 ) following equation (19). A white Zinc Sulphate (ZnSO4) white precipitate is formed after the abovementioned process,…”

“…Some of the relevant literature related to this topic is compared in table 1 to understand the importance of the work under consideration briefly. For example, the electronic switching technology discussed in [19,20] introduces unwanted waveform distortions in the signal output. Wheatstone bridge-based circuit arrangement and resistance changes are adopted in [21,22] to compensate for the temperature-related error in anemometer design by analyzing the data related to fluid velocity and sensor resistance.…”

A 2 MS/s Full Bandwidth Hall System with Low Offset Enabled by Randomized Spinning

“…Hall plates are widely used as magnetic field sensors because they can be easily cointegrated with on-chip readout circuitry in nearly all standard Complementary Metal Oxide Semiconductor (CMOS) technologies. They form a cheap solution for various applications requiring contactless position sensing or galvanic isolated sensing of large electric currents [1][2][3][4][5][6][7]. A well-known disadvantage of Hall plates is their relatively large offsets compared to the weak information signal that is generated by the Hall effect [1,8,9].…”

“…The offset component is still fully present in the Hall plate output signal. Suppression of the offset-related components is in practice performed by means of filtering [11] or an offset reduction loop (ORL) [1,2,[12][13][14][15][16][17][18]. A drawback of such an approach is that, in principle, it prevents the signal bandwidth from extending beyond the chopping frequency.…”

“…In many applications, the potential removal of an in-band signal is not acceptable, which implies that the sensor bandwidth is fundamentally limited by the chop frequency resulting from current spinning. This limitation of the spinning Hall readout can be circumvented by combining the readout from multiple paths [1,2], but this comes at a cost in terms of system complexity and area.…”