Core-less magnetic current sensor still shuns stray fields

Melexis has announced a magnetism-based current sensor that needs no ferromagnetic core, for measuring currents through power PCBs and busbars (see diagram).

MLX91235 is gradiometric, taking a differential magnetic field measurement with two internal sensing elements “ensuring stray field effects are eliminated”, according to the company.

It is aimed at automotive and other e-mobility applications and, as such, has been designed for functional safety, compliant to ISO 26262 as an ASIL B SEoOC (safety element out of context).

“Going beyond ASIL B requirements, it also incorporates a built-in self-test feature that encompasses the complete signal chain,” said Melexis.

Bandwidth is 500kHz and it responds in 2μs.

Inside is digital processing for calibration, thermal compensation and dealing with intrinsic non-linearities.

Better than 0.5% thermal sensitivity drift from -40 to 150°C is claimed, as is better than 1% total sensitivity drift over lifetime from -40 to 150°C.

The temperature value is available externally through the SPI bus in 10bit form, and this bus can also be used by a host processor to trigger the built-in self-test mentioned above – which allows the sensor to report under-voltage and mechanical stress as well as temperature – and to apply certain calibrations.

“Compared to analog core-less sensors, digital calibration provides a more direct and significantly quicker experience, enabling easy adjustment of elements like digital gain correction,” claimed Melexis.

16bit over-current detection is built in, with asymmetric thresholds and two configurable threshold ranges.

Detection time can be configured from 2μs upwards, and there is an optional de-bounce strategy which “helps to avoid false positives in harsher EMC environments”, according to the company.

Packaging is SOIC-8.

Use is foreseen in inverters, dc-dc converters, chargers, electrically heated catalysts, battery management and smart pyro fuses.

Sadly, the data sheet is not public. Find a limited data brief linked from this product page.