Current sensor aids shunt design

Louise Smyth

Melexis has launched a family of calibrated Hall Effect current sensors with low resistive losses that that can be used for more effective shunt designs.

Running off a 5V supply, MLX91210 ICs have current sensitivity levels down to 26.7mV/A and support linear current measurement ranges up to ±75 A (30 Arms).

The MLX91210 family supports both DC and AC current measurements, including precision current flow monitoring in power distribution units of server farms and data centres, power supplies and converters, demand response load control, household/appliance smart metering and energy intelligence, solar power converters and combiner boxes, and electrical motor control in general.

Available in SO8 and SO16 package formats, the fully integrated sensors have extremely low resistive losses (0.8mΩ for the SO8 and 0.7mΩ for the SO16) and provide high voltage isolation ratings (2.1kVRMS and 2.5kVRMS respectively), as well as a fast responsiveness of 5µs. 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.

The key differentiator of the design is minimal magnetic hysteresis, which results from the design not needing a ferromagnetic concentrator. Inside the package, the magnetic field generated by the current flow is sensed differentially by two sets of Hall plates. This architecture reduces the effect of external fields and crosstalk and the close proximity of the Hall plates with the current conductor results in higher signal integrity without compromising the isolation.

“There is greater impetus for compact current/power monitoring in both domestic and industrial environments, with new legislative measures being established for higher efficiencies as well as financial concerns due to escalating energy costs,” said Bruno Boury, Product Line Manager for Magnetic Sensing at Melexis. “These new high speed devices are raising the bar in current sensor technology. Thanks to their compact form factors combining the sensing and isolation mechanism in a few tens of square millimetre footprint with very low ohmic losses, thermal drift compensation features and crosstalk immunity, they can be deployed into concentrated electronic systems and still deliver high degrees of accuracy.”

The family can be factory calibrated for zero-current output point and sensitivity with a temperature range of -40°C to 125°C and the sensors comply with IEC-60950, with the SO16 packaged devices also certified to UL1577.