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Switch IC simplifies Hall-effect sensor system

Posted: 05 Jan 2007 ?? ?Print Version ?Bookmark and Share

Keywords:sensors? Hall effect? power management? interface switch? Allegro?

A6850 interface switch from Allegro

Allegro MicroSystems Inc. has released a dual-channel switch interface IC designed to simplify the implementation of a two-wire Hall-effect sensor system. The A6850 eliminates the need for an external sense resistor and comparator, thereby reducing system costs. The elimination of the sense resistor also results in the subsequent elimination of the voltage drop across the resistor, which can enable sensing systems to operate down to lower battery voltages.

The new device offers two channels integrated on a single IC as well as current clamping, thermal protection and low operating current (SLEEP) mode. The A6850 is rated over a wide operating voltage and temperature range, making it suitable for various automotive sensing systems.

The device uses protected high-side low resistance DMOS MOSFETs to switch the supply voltage to the two Hall-effect devices. Each switch can be controlled independently via individual ENABLE pins and both switches are protected with current-limiting circuitry. The output switches are rated to operate to 26.5V and will source at least 25mA per channel before current limiting.

Integrated current monitor
Typical two-wire Hall sensor applications require the user to measure the supply current to determine whether the Hall sensor is switched on (magnetic field present) or switched off (no magnetic field present). This is usually accomplished by using an external series shunt resistor. The A6850 eliminates the need for the external series shunt resistor by incorporating an integrated current mirror, which reports the Hall sensor supply current as a 1/10 value on the SENSE1 or SENSE2 output pin. A low current SLEEP mode is available (<15?A) by driving both ENABLE pins low. Also, the device can be used to interface with mechanical switches.

Allegro's A6850 is supplied in an industry-standard profile 8-pin Pb-free SOIC package.

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