Green Latch Enables Great Power-Saving For Contact-Less Magnetic Scrolling Applications

September 24, 2009 - Ieper, Belgium. Melexis announces today the release of the MLX92213. This newly designed low voltage Hall-Effect Latch sensor integrates advanced power management providing micropower-efficient solutions for battery or handheld applications. With its ingenious magnetic design, the MLX92213 offers a breakthrough contact-less and reliable solid-state solution for incremental rotary encoders. The device enhances the efficiency and power consumption of all scrolling or trackball-type applications found in computer peripherals, mobile phones or other handheld consumer electronics.

The MLX92213 features an ultra-sensitive Hall-effect Latch operating from 1.6V to 3.6V. The output is a “Push-Pull” type so that an external pull-up resistor is not needed for proper operation, hence reducing PCB component count. The device is primarily targeting battery-operated applications. The MLX92213 employs an awake/sleep strategy to reduce its power consumption versus a standard Hall-Effect latch sensor. This Micropower Hall-effect Latch is ideally suited for use in speed and direction detection applications based on multipole magnets.

Low Voltage Hall-Effect Latch
Produced in a CMOS process, the MLX92213 uses sub-micron technology optimized for low voltage operation suitable for application within 1.6V to 3.6V Vdd range.. Combining Hall element and offset cancellation system, the MLX92213 provides ultra-sensitive, accurate and stable magnetic switching points, independently of temperature and mechanical stress. The output signal is provided directly through a push-pull output with a standard +/-1mA capability eliminating the need for an external pull-up resistor. The device provides contact-less and solid-state switching based on a magnetic solution, therefore offering bounce-free switching, robust operation in dirty and dusty conditions and is not subject to mechanical wear-out. Under power, the device will detect the presence of a magnetic field and switches its output accordingly. When the Hall sensor senses a South magnetic pole of a sufficient strength, the output is latched in a low state. It remains in this state until the Hall sensor senses a North magnetic field of a sufficient strength where the output is then latched in a high state.

Enabling Micropower-Efficient Solution
The MLX92213 features Micropower functionality. It uses a specific awake/sleep cycling strategy to lower its average current consumption. During the Awake cycle, the device powers up the analog circuitry for typically 30 microseconds to perform a magnetic measurement and update the output state. Then the device enters in Sleep cycle for typically 1.3 milliseconds where the output is latched and only the digital part is kept alive, meaning the current consumption is minimal. The resulting cycling reduces the average current consumption below typically 50 microamperes at 3V, almost 30 times lower compared to a standard Hall-Effect Latch. Additionally, The MLX92213 provides a dedicated “Enable” input pin for even more stringent power requirements. When the Enable pin is driven to low state, the device enters into a standby mode, leading to an ultra-low current consumption below 1 microampere. The device can therefore be virtually switched off with a simple logic signal to save even more power without need of fancy system architecture with an additional switch on the supply voltage line. The Enable pin also allows more advanced power management to balance between application and power requirements. By simply “pulsing” the Enable pin, the magnetic field sampling frequency can be increased or decreased to either detect fast-changing magnetic fields above 260Hz or to reduce the average current consumption during operation below 50 microamperes. The MLX92213 offers therefore a high degree of flexibility for demanding applications where power-savings are a primary concern.

Ready for Miniature Design and Massive Production
The MLX92213 device is delivered in a Lead-Free and Green Compliant Micro LeadFrame Package. This miniature package requires only 3mm2 PCB surface (1.5 x 2mm) with only 0.4mm thickness. This represents a major advantage versus any optical solution as it allows producing much thinner application designs for consumer handheld devices such as portable media players or smart phones.