A1128: Highly Programmable Hall-Effect Switch

The A1128 is a field-programmable, unipolar Hall-effect switch designed for use in high-temperature applications. This device uses a chopper-stabilization technique to eliminate offset inherent in single-element devices.

The devices are externally programmable. A wide range of programmability is available on the magnetic operate point, BOP , while the hysteresis remains fixed. This advanced feature allows optimization of the sensor IC switchpoint and can drastically reduce the effects of mechanical placement tolerances found in end-use production environments.

A proprietary dynamic offset cancellation technique, with an internal high-frequency clock, reduces the residual offset voltage, which is normally caused by device overmolding, temperature dependencies, and thermal stress. Having the Hall element and amplifier in a single chip minimizes many problems normally associated with low-level analog signals.

Two package styles provide a magnetically optimized package for most applications. Type LT is a miniature SOT89/TO-243AA surface mount package that is thermally enhanced with an exposed ground tab, and type UA is a three-lead ultramini SIP for through-hole mounting. The packages are lead (Pb) free, with 100% matte tin plated leadframes.

The A1128LLTTR-T package variant is in production but has been determined to be not for new design. This classification indicates that sale of this device is currently restricted to existing customer applications. These devices should not be purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available. Recommended replacement: A1128LUATS-T.


Astrorep Inc. (Allegro and Sanken Semiconductors, Sanken Power Supplies)
141 John Street, Suite 300
Babylon, NY 11702
Phone: (631)422-2500
Fax: (631)422-2504
Web: www.astrorepinc.com
Email: donna.tweedy@astrorepinc.com

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  • Chopper stabilization for stable switchpoints throughout operating temperature range
  • Externally programmable:
    • Operate point (through the VCC pin)
    • Output polarity
    • Output fall time for reduced EMI in automotive applications
  • On-board voltage regulator for 3 to 24 V operation
  • On-chip protection against:
    • Supply transients
    • Output short-circuits
    • Reverse battery condition

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Product Image Functional Block Diagram

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check
Distributor Stock
A1128LLTTR-T 3-lead SOT -40°C to 150°C Yes View Data Not for new design Contact your
local sales rep
Check Stock
A1128LUA-T 3-lead SIP -40°C to 150°C Yes View Data Contact your
local sales rep
Check 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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