Melexis has made a major advance in magnetic sensing technology that will have widespread implications for modern automobile design. Its latest product - the MLX92292 - effectively represents a whole new way of sensing. This device delivers switch and latch functions, but unlike existing products on the market it can determine the presence of magnetic fields that are lateral, not just orthogonal, to it. The uniqueness of this offering is taken further by the fact that the MLX92292 latch/switch is the only one to currently support ASIL B safety integrity level (in accordance with ISO 26262), 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 -90 mT to +90 mT.
Housed in 3-lead TSOT or TO92 package formats, with an operating voltage range encompassing 3.3 V to 18 V, the MLX92292’s extremely low power consumption (typically drawing just 7 µA) makes it highly 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.
Safeguarding the MLX92292 are reverse supply voltage, thermal, electro-static discharge (ESD) and over-voltage protection, plus under-voltage lockout features. With the capacity to deal with a 40 V load dump, it can be connected directly to the vehicle battery - something that is impossible for other Hall effect Latch/Switch solutions. In order to achieve ASIL B compliance, numerous diagnostic/monitoring functions have been incorporated, including sensor element diagnostics and internal voltage references. The device comprises a full set of programmable reporting features, giving it compatibility with any existing electronic control unit (ECU) interface. Only the normal application pins are required for this - dispensing with the need for external diagnostic pins and thus simplifying the design concept considerably.
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