Precision Hall-Effect Switches

By Allegro MicroSystems, LLC 112

Precision Hall-Effect Switches

Allegro's A1120 and A1125 Hall-effect, unipolar switches are extremely temperature-stable and stress-resistant sensor ICs that are especially suited for operation over extended temperature ranges up to 150°C. Superior high-temperature performance is made possible through dynamic offset cancellation, which reduces the residual offset voltage normally caused by device overmolding, temperature dependencies, and thermal stress.

Each device includes on a single silicon chip a voltage regulator, Hall-voltage generator, small-signal amplifier, chopper stabilization, Schmitt trigger, and a short-circuit protected open-drain output to sink up to 25 mA.

An on-board regulator permits operation with supply voltages of 3 V to 24 V. The advantage of operating down to 3 V is that the device can be used in 3 V applications or with additional external resistance in series with the supply pin for greater protection against high voltage transient events.

A south pole of sufficient strength turns the output on for A1120. Removal of the magnetic field turns the output off. The A1125 is complementary, in that for these devices, a south pole turns the A1125 output off, and removal of the magnetic field turns the output on.

  • Unipolar switchpoints
  • Resistant to physical stress
  • Superior temperature stability
  • Output short-circuit protection
  • Operation from unregulated supply
  • Reverse battery protection
  • Solid-state reliability