Magnetic latch / switch meets ASIL B requirements

December 02, 2015 // By Christoph Hammerschmidt
Melexis claims a major advance in magnetic sensing technology that will – according to the company - have widespread implications for modern automobile design. The Belgian Micoelectronics company has developed a device that incorporates a new way of sensing magnetic fields, enabling it to determine the presence of magnetic fields that are lateral, not just orthogonal, to it. Thus, it gives electronics designers more flexibility.

The MLX92292, as Melexis has baptised the new device effectively delivers switch and latch functions. The uniqueness of this offering is taken further by the fact that the latch/switch is the only one to currently support ASIL B safety integrity, with an array of built-in diagnostic mechanisms available.

Flexibility is a key attribute of the MLX92292. OEM customers can choose straightforward pre-programmed units, or alternatively they can benefit from the end-of-line (EoL) programming capacity. Through this each device may be configured (via its output pin) during the OEM production process, so system optimization is fully realized. The programming facility also enables setting of both magnetic operating points to small increments across a range spanning -90mT to +90mT.

Housed in 3-lead TSOT or TO92 package formats, with an operating voltage range encompassing 3.3V to 18V, the MLX92292’s low power consumption of just 7uA makes it suitable for battery-powered operation. This will prove advantageous in circumstances where the vehicle’s engine may not be turned on, as it places no significant drain on the battery resource. As sleep time is a programmable parameter, power consumption can be matched with customers’ specific power budget needs. Target applications include brake lights, steering sensors, handbrake mechanisms, etc.

The MLX92292 can be specified with standard orthogonal sensitivity or the lateral sensitivity option. The upshot of lateral sensitivity being that there is potential to replace multiple devices with a single surface mount unit, thereby saving valuable board space and lowering bill-of-materials costs. This stems directly from Melexis’ proprietary Integrated Magnetic Concentrator (IMC) technology, which enables substantial heightening of signal-to-noise ratios in magnetic field measurement. In addition, the capacity of this technology to sense laterally allows lower profile system implementations, as the magnet can move alongside the device rather than having to be above it.

With the capacity to deal with a 40V load dump, it can be connected directly to the vehicle battery - something that is impossible