A1250 Hall-Effect Latch / Bipolar Switch


The A1250 Hall-effect sensor IC is a temperature stable, stress-resistant bipolar switch. This device is the most sensitive Hall-effect device in the Allegro bipolar switch family and is intended for ring-magnet sensing. Superior high-temperature performance is made possible through an Allegro patented dynamic offset cancellation that uses chopper stabilization. This method reduces the offset voltage normally caused by device overmolding, temperature dependencies, and thermal stress.

The A1250 includes the following 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. Advanced BiCMOS wafer fabrication processing takes advantage of low-voltage requirements, component matching, very low input-offset errors, and small component geometries.

The A1250 Hall-effect bipolar switch turns on in a south polarity magnetic field of sufficient strength and switches off in a north polarity magnetic field of sufficient strength. Because the output state is not defined if the magnetic field is diminished or removed, to ensure that the device switches, Allegro recommends using magnets of both polarities and of sufficient strength in the application.

The A1250 is rated for operation in the ambient temperature range L, –40°C to 150°C. Two package styles provide magnetically optimized solutions for most applications. Each package is lead (Pb) free version, with 100% matte-tin-plated leadframe.

Top Features

  • AEC-Q100 automotive qualified 
  • High-speed, 4-phase chopper stabilization
  • Low operating voltage down to 3 V
  • High sensitivity
  • Stable switchpoints
  • Robust EMC

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
A1250LLHLT-T 3-lead SOT -40°C to 150°C Yes View Data Contact your
local sales rep
Distributor Stock
A1250LLHLX-T 3-lead SOT -40°C to 150°C Yes View Data Contact your
local sales rep
Distributor Stock
A1250LUA-T 3-lead SIP -40°C to 150°C Yes View Data Contact your
local sales rep
Distributor Stock

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.



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