Line of User-Programmable, Two-Wire, Unipolar, Hall-Effect Switches

AllegroMicroSystems Inc.'s new line of user-programmable, two-wire, unipolar,Hall-effect switches complement its existing family of devices used in seatbelt buckle, seat position and shift selector (PRNDL) applications. Allegro's A1190/2/3 family consists oftwo-wire, unipolar, Hall-effect switches, which can be trimmed by the user atend-of-line to optimize magnetic switchpoint accuracy in the application. Thesedevices are produced on the Allegro advanced BiCMOS wafer fabrication process,which implements a patented high frequency, 4-phase, chopper-stabilizationtechnique. This technique achieves magnetic stability over the full operatingtemperature range, and eliminates offsets inherent in devices with a singleHall element that are exposed to harsh application environments.

TheA119x family has a number of automotive applications. These include: sensingseat track position, seat belt buckle presence, hood/trunk latching and shiftselector position. Two-wire unipolar switches are advantageous incost-sensitive applications because they require one less wire for operationversus the more traditional open-collector output switches. Additionally, thesystem designer inherently gains diagnostics, because there is always outputcurrent flowing, which should be in either of two narrow ranges. Any currentlevel not within these ranges indicates a fault condition.

Anupgrade to this family of two-wire switches is the on-chip transient protectionand a zener clamp to protect against over-voltage conditions on the supplyline. This improved high voltage transient protection allows these devices tosurvive ISO 7637-2 and 40 V load dump for <0.5 secs with minimal,and sometime no, protection from discrete components. The ESD protection hasbeen enhanced, such that these devices are capable of handling transients up to8 kV Human Body Model (HBM). The A1190, A1192 and A1193 are offered in aSOT-23W style, miniature low profile package (LH) for surface-mountapplications. All devices are priced at $0.56 in quantities of 1,000.

Line of User-Programmable, Two-Wire, Unipolar, Hall-Effect Switches