Melexis unveils fully integrated inductive switch

It enables small module designs with reduced component count for improved safety and electrification: high voltage interlocks, charging flaps, seatbelts, hood/trunk, gear tooth sensing, or brake-by-wire applications.

For traditional safety automotive latches and switches, ranging from door and boot/trunk handles to seatbelts and brake light switches, the standard design uses a mechanical contact or magnetic switch, like a push button, reed switch, or hall effect sensor. But for such a solution to operate, the safety target’s design must be modified, either to include a magnet plus holder or a physical protrusion to actuate a button.

With Melexis’ induction solution, this is no longer the case. Its technology instead actively senses the actual safety target, such as a seat belt buckle or door latch, directly without a magnet or button actuator, provided it is conductive.

This shift in position-sensing technology comes with several benefits. With no moving mechanisms or additional parts, reliability, and safety are enhanced with the direct sensing operation not tied to parts affixed to the safety element that could become damaged or displaced. Furthermore, the solution helps to reduce the bill of materials (BOM) and the inductive contactless operation is inherently more reliable than mechanical solutions which wear over time, as well as being immune to magnetic disturbance.

State-of-the-art design

Central to the MLX92442 is its heavily integrated and miniaturised standard packaging. Melexis's design innovates by fully integrating the coils and interface within the chip, removing the need for engineers to develop bulky PCB and coil solutions for their application.

The solution is available in through-hole VK packaging or surface-mount SOIC packaging. In either case, the supporting BOM is reduced from three to two elements (target + IC/coils) compared to existing solutions, and this, combined with the foregoing magnets, helps to produce a more sustainable and safer design than existing sensors on the market.

Ensuring continued and reliable operation, the MLX92442 also includes reverse supply voltage, under-voltage, and thermal protection, as well as an advanced integrated self-diagnostic function with a dedicated safe mode.

Streamlined integration

Besides reducing the BOM component count, Melexis’ inductive solution helps to streamline development time. Both factory and end-of-line programming are supported, and the smart switch/latch operation is established by simply defining the applications’ shape and motion. In contrast to Hall effect solutions, magnetic simulation is not necessary, resulting in saved development time (next to BOM savings).

In terms of assembly design, the standard packaging and lack of magnets plus holder allows for simpler system integration. It streamlines the supply chain, with fewer elements helping to reduce both prototyping and production assembly time. This factor also helps to maintain mechanical tolerances in assemblies, as only the inductive sensor and conductive safety element need to be considered within air gaps up to 1.5mm.

With industry standard two or three wire interfaces, a wide operating voltage of 3.5V to 18V, a working temperature window of –40°C to 150°C and ISO26262 ASIL A compliance, the MLX92442’s design considerations are minimal. Furthermore, for safety-critical applications requiring heterogeneous redundancy, the inductive technology provides a highly reliable option with minimal design requirements that can operate next to the Hall effect and mechanical solutions.

Ready for evaluation

“With this new technology, our engineering teams have redefined end-position sensing, delivering a wide range of benefits,” said Minko Daskalov, Product Manager at Melexis. “Induxis is there to enable the next step in electrification and safety, with battery and hydrogen technologies for both the grid or EVs. The MLX92442 ticks all the right boxes”

The MLX92442 is currently in pre-production with engineering B-samples and evaluation kits available.