Hall-effect current sensing replaces shunt-resistive measurements

July 17, 2016 // By Graham Prophet
These high speed isolated calibrated current sensors are presented as an effective alternative to conventional shunt based solutions; standard-footprint packaged ICs simultaneously offer 100 kHz bandwidth, high accuracy and crosstalk resilience

Melexis (Tessenderlo, Belgium) has added the MLX91210 family of integrated sensors; operating from a 5V supply, the ICs have current sensitivity levels down to 26.7 mV/A and support linear current measurement ranges that span as far as ±75A corresponding to 30 ARMS current. Available in SO8 and SO16 package formats, these fully integrated Hall-effect current sensors have extremely low resistive curent-path losses (0.8 mΩ for the SO8 and 0.7 mΩ for the SO16) and provide high voltage isolation ratings (2.1 kVRMS and 2.5 kVRMS respectively), as well as accelerated responsiveness (within 5 µsec). The sensor output of each IC is factory-calibrated for a specific current range and compensated for optimal stability in relation to temperature and over the course of its working lifespan, so that long term accuracy is maintained.

With provision to be factory calibrated for zero-current output point and sensitivity, these devices produce a linear analogue output that is proportional to the current flowing directly through the IC’s leadframe. Inside the IC package, the magnetic field generated by the current flow is sensed differentially by two sets of Hall plates. This configuration combats the effect of external fields and crosstalk. The close proximity of the Hall plates with the current conductor results in superior signal integrity, but at the same time a strong insulation layer separates the primary and secondary sides. The devices exhibit strong robustness against external fields. A key differentiator is the virtually non-existent magnetic hysteresis, which results from the design not requiring a ferromagnetic concentrator. Temperature range is -40°C to 125°C and the sensors comply with IEC-60950 (SO16 packaged devices adhere to UL1577).