Re-programmable 2-wire Hall switches simplify system design

May 23, 2014 // By Graham Prophet
Melexis Technologies’ MLX92242 Hall effect switch/latches are highly integrated devices containing a voltage regulator (supporting a wide operating voltage range), as well as Hall sensing element and a current sink-configured output driver, in a single low-profile package.

Programmable memory is used to enable the various tolerances that need defining for a specific application to be set (via the device’s VDD pin) and if necessary readjusted, before finally being locked. The range and resolution of programmable magnetic thresholds and thermal sensitivity coefficients allows the sensor working in conjunction with a magnet to easily implement a ferrous metal proximity sensing system. The temperature compensation programmability of the MLX92242 means it can be used with all kind of magnets (including the low cost ferrite materials). The resulting cost-effective and very small ferrous proximity switch handily serves many limit position, proximity detection and encoding applications.

What differentiates the MLX92242 from other devices of this kind is that it supports 2-wire rather than a 3-wire implementation, only needing use of the VDD and GND pins, but still providing all the necessary diagnostic capacity to respond if malfunction conditions occur. The advantage of this is that less wiring/cable harnessing is needed, allowing deployment into confined spaces and reducing the overall weight in applications where this could otherwise be a disadvantage. The voltage range covers 2.7V to 24V.

The MLX92242 is mainly targeted at automotive applications, such as seatbelt latch detectors, seat position sensors, window lifters, etc. It can be implemented in remote applications, where it is some distance from the electronic control unit (ECU). A variety of industrial and security based tasks can also benefit from its use. The sophisticated proprietary offset cancellation system within the magnetic core enables faster and more precise processing of the data acquired from the sensing element while being resilient to the temperature fluctuations and other forms of stress that are inherent in automotive and industrial environments. The device has a very high resilience to electro-static discharge (ESD) phenomena, with 8 kV human body mode ESD compliance, and has a broad operational temperature range which spans from -40°C to 150°C. Reverse supply voltage and under-voltage lockout protection mechanisms