Hall Latch Manages Extreme Environments

June 21, 2010 - Ieper, Belgium - Melexis releases the MLX92211, second generation of Automotive Hall-Effect Latch sensors. The MLX92211 comes as a great successor of the worldwide famous USx88x series by Melexis. This brand new platform has been meticulously designed to deliver a standard product with tremendous performance and exceptional robustness for more and more stringent automotive requirements such as Electrical Power Steering (EPS), Window lifters/Sunroof, Seat Adjusters, Wipers or Motor Commutation.

The MLX92211 features a very sensitive Hall-Effect sensor operating from 2.7 to 24 volts, covering automotive, consumer and industrial applications. With Latching magnetic behavior, the open drain output is switched ON and OFF by applying South and North magnetic field perpendicularly to the package top side, typically the case with rotary applications using “on-shaft” multi-poles ring magnet.

Especially designed for automotive applications, the device integrates all protections required when using “integrated” or “remote” sensors like very high electro-static discharge (ESD) rating, reverse supply voltage protection, output short circuit protection and even more.

Brand New Platform
The MLX92211 core is based on a high voltage sub-micron process ideally suited to handle low and high operating voltage from 2.7 to 24 volts as well as low and high operating temperature from -40 to 150 degree Celsius.

The whole magnetic core was reinvented in this platform with a special focus on the offset cancellation system to allow faster and more accurate processing while being temperature insensitive. A negative temperature coefficient of -1000ppm/degC was implemented to compensate the natural behavior of magnets becoming weaker with rise in temperature.

The result leads to very stable and accurate magnetic switching points of typically +/-3mT (milliteslas)at 25degC, while the output is updated every 6us (micro-seconds) with a jitter of only +/-3us, thus increasing repeatability factor within the application.

Technical Jewel for Automotive
Based on years of a proven automotive expertise with the well-known USx88x series, the MLX92211 has been created with one major objective: “Designed for Automotive”.

In the first line, very high ESD rating up to 4000 volts (Human Body Model) on each pin brings a comfortable safety margin against potential ESD stress occurring either during module assembly or usage. The built-in reverse supply voltage protection best protects the device against incorrect connection of the supply line which is quite important in case of “remote” sensors.

The open drain output is also well protected with integrated current limitation in the event where a short circuit would directly occur between the supply voltage and the output pin with the output driver being switched ON.

Using long cable in automotive in inherently source of interference on the supply line. A conventional Hall sensor can be sensitive to supply voltage variation nearly the minimum operating voltage as it could perturb the magnetic measurement cycle, resulting in an unexpected output toggling. The MLX92211 tackles this issue by including an Under-Voltage Lock-Out. Like for complex microcontroller, this system will freeze the device in case a critical low voltage is reached, hence avoiding unexpected behavior or impulse on the output pin. In the event where the output short-circuit protection is activated, the built-in output auto-shut-off automatically detects if this condition lasts for more than 250us (microseconds), meaning the failure is permanent without sign of recovery. If so, the output is immediately switched OFF. Then a self-check is periodically performed every 3.5ms (milliseconds) by switching ON the output driver to test if the short-circuit failure is released. Since running into failure mode shortens lifetime of a product, this ingenious protection increases the reliability of the device by avoiding to be kept into failure mode until manual intervention. This cycling can also be used within the application to detect the presence of a short-circuit condition and take appropriate measure (raise flag or else).

Last but not least, the device has been extensively tested and qualified according strict automotive Electro-Magnetic compatibility requirements, showing outstanding performance and immunity within harsh environment.

Packaging & Availability
The MLX92211 is packaged in the 3-pin Thin SOT (TSOT) package for SMD mounting – “SE” package code. This package has been specially selected with a particularly to be “face-up” meaning the silicon die is facing the package top side. This allow to bring the Hall sensor element closer to the package top, hence reducing total effective air-gap which might be quite critical for some applications.

Respectful of the environment, the SE package is fully “Green” compliant including notably RoHS (Restriction of Hazardous Substances), Lead-Free (Pb-Free) and Halogen-Free compliance.

The device is available for high volume production with engineering samples available on request.