2D speed & direction sensor IC uses vertical & planar Hall elements

Posted By : Jordan Mulcare
2D speed & direction sensor IC uses vertical & planar Hall elements

The A1262 from Allegro MicroSystems Europe is a unique dual-channel Hall-effect latch featuring 2D sensing via a combination of vertical and planar Hall elements. The quadrature outputs of the A1262 allow rotation direction and position to be determined in applications such as sensing a rotating ring-magnet target. The unique 2D operation of the combined planar and vertical Hall elements allows the end user to achieve a suitable 90° of phase separation between channels which is also inherently independent of ring magnet geometry and pole pitch.

Using the A1262, system designers can achieve new mechanical configurations which would not be feasible with traditional planar Hall sensors, including replacing pairs of through-hole single-inline packaged devices with a single, tiny surface-mount SOT23 IC, saving space and cost. 

The device is targeted at motor commutation and rotary position sensing applications in the automotive, industrial and consumer markets. Typical uses include window blinds, garage door openers, scroll wheels, power window lifts, white goods and controls for sunroof, sliding door, car-boot and tailgate motors in the automotive sector.

The Allegro A1262 sensor IC is available in two options that allow flexibility in the magnetic design of end-user systems. Both options feature a planar Hall element that is sensitive to magnetic fields perpendicular to the face of the package (the Z direction). The other signal 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, while 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 a lower total effective air gap than can be achieved with competing solutions.

Each device includes, on a single silicon chip, two Hall plates (one planar and one vertical), a multiplexer, a small-signal amplifier, chopper stabilisation, a Schmitt trigger circuit, and two short-circuit protected NMOS output transistors to sink up to 20mA. The on-board regulator permits operation with supply voltages of 3 to 24V and adds EMC robustness such as greater protection against high-voltage transient events.

The A1262 is qualified to AEC-Q100 automotive 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 overmoulding, temperature dependencies and thermal stress. 

The device is highly sensitive, with a typical magnetic operating switch point (BOP) of 17 G, 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% matte tin leadframe plating. 

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