Allegro MicroSystems Europe - PRODUCT NEWS Ultra-sensitive dual Hall-effect switch IC ideal for direction sensing
The A3425 dual Hall-effect switch from Allegro MicroSystems is an ultra-sensitive dual sensor integrated circuit that is ideally suited to fine-pitch direction-sensing applications in harsh automotive and industrial environments. In operation, the A3425 provides digital quadrature outputs for easy signal processing through the use of precision aligned Hall elements and low-drift BiCMOS circuitry. Typical applications include digital encoder systems for motor controls - in windscreen wipers, power windows and sun roofs, for example. The new device is extremely temperature-stable and stress-resistant, offering reliable operation over extended temperature ranges up to +150°C; This 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 A3425 includes, on a single silicon chip, a voltage regulator, two independent Hall-voltage generators, two small-signal amplifiers with chopper stabilisation, two Schmitt triggers, and two short-circuit protected open-collector outputs to sink up to 30 mA each. An on-board voltage regulator permits operation with supply voltages from 3.3 to 26.5 V. With suitable output pull-ups, it can be used directly with bipolar or MOS logic circuits. Allegro MicroSystems has eliminated the major manufacturing problems encountered in fine-pitch direction-detection applications: namely, maintaining accurate mechanical location between the two active Hall elements. In the A3425, the two Hall elements are photolithographically aligned to better than 1 mm, as contrasted with the 100 mm (or more) mechanical location tolerance typical of discrete manufacture. The high sensitivity of the A3425 makes it ideal for use with high-density magnets. The spacing of 1 mm between the two elements means that the device will maintain perfect quadrature with a magnet-pole spacing of only 2 mm. The A3425 dual Hall-effect switch is supplied in a 4-pin plastic single inline package for operation over a temperature range of -40°C to +150°C. __________________________________________________ Allegro MicroSystems Europe
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Ref: Allegro002August 2000
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