Allegro MicroSystems, Inc. Introduces a New Family of Two-Wire, Hall-Effect Unipolar Switches Improved High Voltage Transient Protection

Allegro’s A1152/3/5/6 devices are the next generation of two-wire, unipolar, Hall-effect switches; factory trimmed to optimize the accuracy of the magnetic switch points. These devices employ a patented, high frequency, four-phase, chopper-stabilization technique to achieve magnetic stability over temperature and to eliminate offset inherent in single-element devices, when exposed to harsh automotive environments. Additionally, this advanced chopping technique provides significantly reduced jitter and faster power-on time.

Commonly found in a number of automotive applications, the A1152/3/5/6 devices are utilized to sense: seat track position, seat belt buckle presence, hood/trunk latching, steering lock position, and in shift selectors. Two-wire, unipolar switches require one less wire for operation versus the more traditional open-collector output switches. Additionally, the user gains diagnostics, as there is always current at one of two specified levels. Any output current outside of these two narrow ranges is a fault condition.

An important upgrade to this family is the on-chip transient protection and a Zener clamp to protect against over-voltage conditions on the supply line. This improved high voltage transient protection allows these devices to survive ISO 7637-2 and 40 V load dump for <0.5 seconds with minimal, and sometime no, protection from discrete components. The ESD protection has been enhanced, such that these are capable of handling a transient of 8.0 kV Human Body Model (HBM).

All family members are offered in two package styles: the “LH” is a SOT-23W style, miniature low profile package for surface-mount applications, and, in the coming months, the “UA” is a TO-92 style, three-lead, ultra-mini, Single Inline Package (SIP) for through-hole mounting.