The new A1152/3/5/6 from Allegro MicroSystems Europe are a range of two-wire unipolar Hall-effect switches designed for automotive sensing applications in seat-belt buckle, seat position, and steering lock applications.

The new devices are produced using the company’s advanced BiCMOS wafer fabrication process, and include improved high-voltage transient protection: a critical factor for automotive applications where external protection circuitry cannot be located close to the sensor.

The switches are factory trimmed to optimise the accuracy of the magnetic switch points, and employ a patented high-frequency four-phase chopper-stabilisation technique to achieve magnetic stability over temperature and to eliminate the offset inherent in single-element devices, when exposed to harsh automotive environments. The advanced chopping technique also provides significantly reduced jitter and shorter power-on times.

The switches require one less wire for operation than more traditional open-collector output switches, and also offer diagnostic capability as there is always current present at one of two specified levels. Any output current outside these two narrow ranges is a fault condition.