Hall current sensing
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Hall current sensing
According to different transformation principles, there are current sensing based on Hall effect, electromagnetic induction based, fluxgate based and so on. Different principles have the same goal, which is to convert a large current into a small current of the same frequency and phase to facilitate measurement or isolation.
The most classic of them is the Hall current sensor, which uses the Hall magnetic balance principle to measure various types of current. Input the measured current at the control current terminal of the Hall element, and at the same time apply a magnetic field in the normal direction of the Hall element plane, so that a Hall potential will be generated at the output end of the Hall element, and the waveform of this potential is consistent with the input current. Therefore, the change of the measured current can be accurately reflected.
Whether it is an open-loop current sensor or a closed-loop current sensor, the basic performance is not much different, mainly depends on whether it can achieve high precision and low drift. In addition to these performance characteristics, isolated sampling is also gaining more and more attention.
MPS current sensor
MPS' MCS18xx current sensor family provides high current monitoring and high isolation voltage between the high current side and the low voltage side of system communication. The load current is sensed by the Hall sensor and displayed as a linear analog voltage proportional to the load current. The CS18xx current sensor family is immune to stray magnetic fields, significantly improving the accuracy of the sensor; and uses an isolated bidirectional Hall effect to sample AC or DC current, and its sub-1mohm resistive conduction path minimizes power loss and increases efficient.
The MCS1800 is a 3.3V single-supply current sensor in this series. The primary conductor with low resistance allows current to flow near the IC containing the high-accuracy Hall-effect sensor. The magnetic field generated by the current is generated by the integrated Hall-effect sensor in two different point sensing. The magnetic field difference between these two points is then converted into a voltage proportional to the applied current. Because of the differential sensing, the MCS1800 can cancel any external magnetic field interference, and the accuracy is greatly improved.
The MCS1800 can measure current ranges of ±12.5A and ±25A, with an accuracy of ±3% over the full temperature range, an internal on-resistance of only 1.xn--2m-fcc, and an adjustable bandwidth of up to 100kHz. In measurement, the MCS1800 can achieve an output rise time of 4μs, and the entire sensor does not have a magnetic hysteresis, which is rare for a current sensor.
The 200VRMS operating voltage can achieve basic isolation, and the shielding is also integrated between the current conductor and the wafer to suppress capacitive coupling (up to 10V/ns), so the isolation greatly reduces the use of existing standard external components. This also saves package size, which is in line with today's small package requirements.
Other models of this series are mainly different in current measurement range, and are similar in shielding of external magnetic field, control of output rise time and isolation configuration. The overall accuracy is controlled within ±2.5% to ±3%, and the primary on-resistance is controlled within 0.9-1.xn--2m-fcc.
TI current sensor
TI's current sensor is also based on the Hall effect, high precision and low drift can be said to be the signature of TI's current sensor. Its current sensing can achieve accurate current measurement regardless of changes in time and temperature. At the same time, the isolated Hall current sensor can significantly prolong the life of the sensor.
The TMCS110X series can be said to include TI's excellent current sensing products. Starting with the TMCS1100, this model is an industry-leading zero-drift high-accuracy current sensor that exhibits excellent linearity and temperature stability, achieving < 1% full-scale error over the entire temperature range of the device.
To make the high precision a little more detailed, it is a signal bandwidth of 80kHz, a sensitivity error of ±0.3% over the full temperature range, an offset voltage error of ±10.5mA, an offset current drift of 0.01mA/°C, and a linearity of 0.1%. In terms of high precision alone, there should be no more extreme performance than this.
The slightly higher on-resistance may be an indicator that the series is slightly behind. 1.xn--8m-fcc is indeed a little dazzling when other indicators are so good, but it definitely belongs to the "low" category. Low on-resistance minimizes power loss and heat dissipation. Therefore, when analyzing the power loss and heat dissipation of the current sensor, the on-resistance value can give a great reference.
The entire family of current sensors has multiple sensitivity options, and the output voltage is proportional to the input current. The fixed sensitivity allows the TMCS110X to operate from a single supply, thus eliminating ratiometric errors and improving supply noise rejection.
This series also provides unidirectional and bidirectional sampling. Bidirectional sampling still has isolation protection. The inherent galvanic insulation provides 600V basic working isolation voltage and 3kV dielectric withstand isolation voltage between the current path and the circuit. This integrated electrical Shielding provides excellent common mode rejection and transient immunity protection.