The new A1172 from Allegro MicroSystems Europe is a sensitive micropower Hall-effect switch with complementary, latched digital outputs and omnipolar magnetic actuation. The new device features operation at low supply currents and voltages, making it suitable for battery-operated electronics. The combination of a low operating supply voltage (1.65 V to 3.5 V) and a good clocking algorithm assists in reducing the average operating power consumption to less than 15 mW with a 2.75 V supply.
The A1172's both north and south polarity magnetic fields of sufficient strength activate output switching to either 'off' or 'on'. The A1172 incorporates two push-pull outputs configured so that one output switches off in the absence of sufficient magnetic field while the other output switches on in the absence of a magnetic field. This polarity independence, as well as the minimal power requirement, can allow the A1172 to replace reed switches, providing high reliability and ease of manufacturing while eliminating the requirement for signal conditioning.
The A1172 includes, on a single silicon chip, a Hall-effect voltage generator, a small-signal amplifier, chopper stabilisation circuitry, a latch, and a MOSFET output. Chopper stabilisation provides improved stability through dynamic offset cancellation, reducing the residual offset voltage normally caused by device over moulding, temperature dependence and thermal stress. This new device is designed to offer a magnetically optimised solution for battery-operated, consumer equipment and is available in a 4-pin wafer level chip scale package measuring 1 x 1 x 0.5 mm. This package reduces the printed circuit board area consumed by these switches.
