Measuring electrical current in a conductor is critical to many systems. 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 new, improved MLX91209CA from Melexis can be applied in all current sensing situations. This high speed Linear Hall IC, which features a programmable sensitivity range from 5 to 150mV/mT, is suitable for measuring DC and AC currents up to 200kHz.
This device features a strong thermal and lifetime stability that is claimed to provide fully programmable critical characteristics – allowing one single part to meet a wide variety of current sensing applications. Parameters such as sensitivity and offset are stored in an internal EEPROM memory. Calibration is achieved using the company’s PTC (Programming Through Connector) protocol. This is said to modulate the supply voltage and does not require any additional pin for programming, enabling efficient production flows. A linear analogue output permits use of the sensor in applications where a very fast response of 3µs is required.
The company advises, 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 this new device is said to be greater than ±0.5 percent at room temperature or ±2 percent 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, RoHS compliant lead-free package.
Demand for current sensing solutions is growing rapidly with the increased proliferation of alternative vehicles, like Hybrid Electric, Electric and Start/Stop equipped ‘Mild Hybrids’. Battery management systems rely on accurate and stable current sensing to control the charge/discharge cycles. Proper management of the current in and out of modern batteries is essential for safety, battery service life and, in full electric vehicles, predictable range calculation.
Continued investment in Solar Power generation and other grid connected energy sources demand accurate and stable monitoring to safely operate on the rapidly expanding ‘Smart Grid’. Here, once again, current sensing is key to the control systems, for the effective integration of small to medium scale power generation systems.
In addition, current sensing is instrumental in the management of power in more traditional electronic systems. Power distribution systems in large scale server installations rely on current sensing to deliver high levels of up-time and predictive maintenance.
Melexis
