Bipolar switch optimised for pulsed power

The A1205, a general-purpose Hall-effect bipolar switch, is optimised for applications in which pulsing the supply line helps conserve power. Allegro MicroSystems Europe’s device is a next-generation replacement of the company’s A3134 bipolar switch. Its claims is that it brings greater performance in a more compact package.

The device is designed to switch in response to a north/south alternating magnetic field, typically from a multi-pole ring magnet. Its hysteresis characteristics ensure clean switching of the output, even in the presence of external mechanical vibration and electrical noise. The biCMOS continuous-time switch features a very short power-on time and lownoise operation.

Device programming is performed after packaging to ensure increased switchpoint accuracy. This is done by eliminating offsets induced by package stress. Unique Hall-element geometries and low-offset amplifiers help to minimise noise as well as reduce the residual offset voltage. Such offset voltage is often caused by device overmoulding, temperature excursions, and thermal stress.

On a single silicon chip, the switch incorporates a voltage regulator, Hall voltage generator, small-signal amplifier, and Schmitt trigger, as well as an NMOS output transistor. Thanks to an integrated voltage regulator, operation can range from 3.8 to 24 V.

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