Magnetic Latch and Switch: Experience matters

By Dieter Verstreken, Melexis

As our world becomes more technology-driven and automated, the role of basic sensors becomes ever more important. More and more systems, including vehicles, household white goods and industrial installations rely on sensing to operate correctly and safely.

As improving the safety of vehicle occupants receives ever greater emphasis, automotive engineers are deploying sensing devices that deliver increased sophistication and raise performance benchmarks. A multitude of different design and integration requirements must be met. For the humble sensor this means that they must be easy to specify/use, they must be small, low power and light as well as being low cost.

Engineers are seeking out companies that can show a long history in serving and understanding the market as well as an innovative approach to solving the problems of today - and tomorrow.

Latch and switch devices rely on the principles of the Hall-effect to, through the position of a magnet, determine the physical position of an object. These on-off switching devices are very common in automotive applications such as braking, shifter applications, doorlocks or seatbelts. However, they are equally valuable to ensure the door of a washing machine is closed, BLDC motor commutation or ensuring that a safety interlock is in place on an industrial machine.

Melexis was founded more than a quarter-of-a-century ago, in 1989. During its early years the company was developing a general-purpose product line based upon CMOS technology and their pioneering work on TSOT packaging.

In 1997, Melexis acquired US MicroChip; the fusion of IC know-how and Hall-effect technology spawned a product range that is now in its third generation and has shipped billions of these units into safety-critical applications across the globe. Decisions taken in 1993 to focus on CMOS technology and TSOT packaging are just as valid today as they were then.

Around 1999, Melexis shifted a little from their general-purpose roots and focused more in automotive. Shortly after the US MicroChip acquisition the first-generation devices were qualified to AECQ for automotive applications, creating a market opportunity that Melexis has serviced from the perspective of a leader ever since.

Second-generation development was started in 2009 with the goal of delivering even greater performance and accuracy. By 2011, an EEPROM was integrated delivering unprecedented flexibility to the range where standard products are manufactured in millions.

Magnetic latch and switch - Melexis

The integrated EEPROM allows key thresholds and compensation to be programmed into devices while on the production line, effectively delivering a custom solution without cost penalties. By programming compensation curves, the devices can be used effectively with low-cost magnets thereby lowering the total cost of the sensing solution.

The EEPROM programming enables high accuracy performance by programming the magnetic operating and release points (including temperature compensation) after packaging). The resulting flexibility allows customers to finetune the sensor settings based on the specific application parameters.

Shortly after, in 2012, the first 2-wire sensor (with EEPROM) was launched to the market. In 2013, Melexis then introduced a customer-programmable 3-wire design bringing flexibility to the field as well as the factory.

The first ASIL A ready design was launched in 2014. The high reliability solutions targets automotive applications and features an integrated capacitor for PCB-less installation in the tightest spaces - as often required in automotive use cases such as seatbelt and transmission applications.

Decisions taken in 1993 to focus on CMOS technology and TSOT-packaging are just as valid today as they were then.

Just a year later, in 2015, ASIL B readiness was achieved and the first micropower devices that allow always-on sensing on vehicles without the risk of draining the battery were launched. Completing a year of significant steps, in 2015, Melexis introduced their Triaxis® technology on the latch and switch product line that offers a whole new way of sensing based upon proprietary Integrated Magnetic Concentrator (IMC™) mechanism. The ability to sense lateral or orthogonal magnetic fields brings the potential to replace multiple devices with a single sensor saving valuable space and reducing BOM costs - which is allowing the customer to make small modules (thereby migrating from through-hole assembly to surface mount reflow).

2016 saw expanded lateral sensing on second generation devices, while dual die made their first appearance in 2017.

The application-specific flexibility throughout the broad product range makes Melexis the first choice when the need arises to upgrade legacy designs to the latest performance standards.

Melexis' newest device, the MLX92292 IC, delivers latch and switch functions and also incorporates many of the features described in this insight, including Triaxis®. The uniqueness of this product is enhanced due to the fact that the MLX92292 IC latch/switch is the only such device to currently support the ASIL B safety integrity level (in accordance with ISO 26262), with an array of built-in diagnostic mechanisms available.

While inherently very basic devices, Melexis' extensive latch and switch range is continually developed to match and exceed the functional, flexibility, safety and power consumption needs of modern applications. The fourth generation is coming; will the planned innovations allow you to improve the safety and convenience of your automotive design?


Inspired Engineering

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