Micronas Develops Dual-Plate Hall Sensor for Automotive Applications

    FREIBURG, Germany, April 2 Micronas
(Swiss: MASN; Neuer Markt Frankfurt: MNSN) announced it has successfully
integrated two Hall plates, the specific sensor elements, on a single Hall
sensor chip at about half the cost of existing solutions.  The new HAL
700 family of sensors is designed for contactless detection of speed and
rotary direction in automotive applications such as sliding roofs, windshield
wipers, seat adjusters and power windows.
    Previously, measuring speed and direction meant that systems manufacturers
had to meticulously align two separate Hall sensor chips at precisely the
required distance and position.  Integrating two Hall-plates on one chip
instead eliminates this error-prone alignment process, which significantly
increases overall system reliability.  The one-chip solution also eliminates
the need for external logic circuitry and will cost about 50 percent less than
two independent sensors.
    "The benefit of Hall sensors over conventional mechanical methods is the
ability to detect speeds and positions without physical contact," said Ronald
Gampp, market manager sensors at Micronas.  "This makes sensors immune to
mechanical wear and environmental contaminants such as dirt, vibration and
great temperature variations, resulting in a much higher level of reliability,
which are especially crucial in applications relevant to car and passenger
safety."
    The two integrated Hall plates enable a sensor to detect if a wheel or
shaft moves forward or backward by detecting the magnetic fields of
multi-polar, rotating ring magnets.  Because Micronas added logic circuitry in
its HAL 710 sensor, it can measure both speed and direction of the rotation
without the need for external logic circuitry.  The on-chip circuitry
determines the direction and speed in which the permanent magnet rotates and
transmits the information through the output pins.
    Hall sensors based on silicon technology supply very low signal voltages.
To amplify those low voltage levels without distortion, the offset has to be
kept to a minimum.  The solution Micronas developed to address this problem
was the chopper compensation technique, which constantly rotates the current
flowing through the Hall plate.  Micronas' sensors create a pure measured
value by rotating the direction of the current about 100,000 times per second.
The result is a very precise device, with maximum two percent deviation, that
can function flawlessly over a temperature range of -40F (-40 degrees C) to
284F (+140 degrees C) with strong long-term stability.
    The HAL 700 and the HAL 710 are available in 4-pin SOT89B packages.
Prototypes are currently available and high volume production will start in
the fourth quarter of this year at prices below US $0.50 for volume orders
over 500,000 units.

    About Hall sensors
    Hall sensors are based on the Hall effect, named after its discoverer
Edwin Hall in 1879.  A Hall element, a square shaped semiconductor layer, for
example, is supplied by a constant current.  When applying a magnetic field
perpendicular to the current flow, the charge carriers are deflected due to
the Lorentz force.  This deflection can be measured as the so-called Hall
voltage, which is perpendicular to both the magnetic field and the current
flow.  The Hall voltage is directly proportional to the magnetic field.

    About Micronas
    Micronas (Swiss: MASN, Neuer Markt Frankfurt: MNSN), a semiconductor
company group with worldwide operations, is a leading supplier of cutting-edge
IC and sensor system solutions for consumer electronics, multimedia and
automotive electronics.  The holding is headquartered in Zurich (Switzerland).
Currently, the Micronas group employs over 1400 people.  In 2000, it generated
over CHF 490 Million in sales.  For more information on Micronas and its
products, please visit http://www.micronas.com.