Programmable linear Hall sensor measures DC and AC currents to 200 kHz
Introducing the MLX91209CA, which follows on and is an upgrade of the 91205 and 91208 variants, Melexis notes the universal challenge of measuring current, preferably without the losses of shunt-based techniques. Classic measurement techniques use shunt resistors, current transformers or magnetic field sensors. Hall effect sensors are frequently the choice when measuring DC currents. However the uprated MLX91209CA can be applied in all current sensing situations, the company says, as the fastest Hall current sensor available; its underlying response time is improved to under 2 µsec from the 6 µsec of its predecessor. The sensor has internal, switchable filtering but even with this applied, it is as fast as previous parts without filtering.
It features thermal and lifetime stability as a foundation for fully programmable critical characteristics – allowing one single part to meet a wide variety of current sensing applications. It achieves very small offset drift of under 10 mV (-40-125°C), and very small sensitivity drift of typically under 100 ppm/°C (-40-125°C). Stability is in part due to use of stress-compensation techniques within the device and packaging.
Parameters such as sensitivity and offset are stored in an internal EEPROM memory. Calibration is done using Melexis’ PTC (Programming Through Connector) protocol. This modulates the supply voltage and does not require any additional pin for programming, enabling the most efficient production flows. A linear analogue output permits use of the sensor in applications where a very fast response of 3 µsec is required.
Custom calibration is best performed in-situ after the sensor is fixed with respect to the current conductor and ferromagnetic core so that a calibrated current sensitivity is achieved. Typical accuracy of a current sensing system based on the MLX91209 is better than ±0.5% at room temperature or ±2% over the full temperature range (from -40°C to 125°C) when applying in-circuit end of line calibration. The device is supplied in a 4-pin SIP package.
You might use the part, Melexis says, for current measurement in vehicle formats such as hybrid electric, electric and start/stop equipped ‘mild hybrids’. The company also sees an upswing in i-BSG, or integrated belt start generator, developments, where an uprated alternator/motor delivers a form of energy reserve similar to motor-racing’s KERS, recovering regenerative braking energy and delivering extra torque when required via the alternator belt. Other growing applications areas are photovoltaic power generation and precision power management in general.
Melexis; www.melexis.com/91209
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