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2D sensor uniquely combines planar, vertical Hall elements

06 Nov 2015

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Allegro MicroSystems LLC has introduced a dual-channel Hall-effect latch featuring 2D sensing via a combination of vertical Hall and planar Hall elements. According to the company, the quadrature outputs of the A1262 allow rotation direction and position to be determined, such as when sensing a rotating ring-magnet target.

The unique 2D operation of the combined planar and vertical Hall elements allows the end user to achieve an ideal 90° of phase separation between channels that is inherently independent of ring magnet geometry (pole pitch), added Allegro. This enables system designers to achieve novel mechanical configurations not feasible with traditional planar Hall sensors, including replacing through-hole SIP devices with tiny surface-mount SOT23 ICs, saving space and cost.

This device is targeted at applications in the automotive, industrial and consumer markets such as motor commutation and rotary position sensing, e.g., window blinds, garage door openers, scroll wheels, power window lifts, sunroof/sliding door/trunk/tailgate motors, white goods, etc.

A1262

The A1262 is available in two options that allow flexibility in end-system magnetic design. Both options feature a planar Hall element that is sensitive to magnetic fields perpendicular to the face of the package (Z). The other channel comes from a vertical Hall element that is sensitive in either the X or Y direction. The Y option features a vertical Hall plate that is sensitive to magnetic fields parallel with the face of the package across the leaded edges of the package. The X option features a vertical Hall plate that is sensitive to magnetic fields parallel with the face of the package across the leadless edges of the package, resulting in lower total effective air gap than can be achieved with competing solutions.

On a single silicon chip, the device includes: two Hall plates (one planar and one vertical), a multiplexer, a small-signal amplifier, chopper stabilisation, a Schmitt trigger and two short-circuit-protected NMOS output transistors to sink up to 20mA. The on-board regulator permits operation with supply voltages of 3V to 24V and adds EMC robustness such as greater protection against high voltage transient events. The A1262 is qualified to AEC-Q100 standards and includes Zener clamps, output short-circuit protection and reverse-battery protection. Superior high-temperature performance is made possible through dynamic offset cancellation, which reduces the residual offset voltage normally caused by device overmolding, temperature dependencies and thermal stress.

Functional block diagram

Functional block diagram

The device is highly sensitive (BOP = 17G typical) and its magnetic operating characteristics are specified across the operating voltage and temperature ranges. Package designator LH5 is a modified SOT23-W surface-mount package, magnetically optimised for a variety of orientations. This package is lead (Pb) free, with 100 per cent matte-tin lead frame plating.




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