A1331: Precision, Micro Power Hall-Effect Angle Sensor IC With Integrated Turns Counter


This part is discontinued. Samples are no longer available. Date of status change: December 5, 2018.

The A1331 is a 360° angle sensor IC that provides contactless high resolution angular position information based on magnetic Circular Vertical Hall (CVH) technology. It has a system-onchip (SoC) architecture that includes: a CVH front end, digital signal processing, and a digital (SPI) output. The A1331 is ideal for automotive applications requiring high speed 0° to 360° angle measurements, such as electronic power steering (EPS) and throttle systems.

Besides providing full-turn angular measurement, the A1331 supports a Turns Counter function that can operate in Low Power mode. This makes the A1331 ideal for applications where, for example, an automobile is in a “key off” position but steering wheel turns must still be tracked.

The A1331 supports a Low RPM mode for slower rate applications and a High RPM mode for high speed applications. High RPM mode is for applications that require higher refresh rates to minimize error due to latency. Low RPM mode is for applications that require higher resolution operating at lower angular velocities.

As part of its signal processing functions, the A1331 includes automotive grade temperature compensation to provide accurate output over the full operating temperature and voltage ranges. The A1331 also includes EEPROM technology for end-of-line calibration.

The A1331 is available in a 24-pin TSSOP lead free package with 100% matte-tin leadframe plating.

Top Features

  • Contactless 0° to 360° angle sensor IC, for angular position, rotational speed, and direction measurement
  • Dual independent die housed within a single package
  • Circular Vertical Hall (CVH) technology provides a single channel sensor system
  • 12-bit resolution possible in low RPM mode, 10-bit resolution in high RPM mode
  • Angle Refresh Rate (output rate) configurable between 25 and 3200 µs through EEPROM programming
  • Capable of sensing magnet rotational speeds in excess of 7600 rpm
  • SPI interface allows use of multiple independent sensors for applications requiring redundancy
  • EEPROM programmable angle reference (0°) position and rotation direction (CW or CCW)
  • Absolute maximum VCC of 26.5 V for automotive battery-powered applications
  • Turns Counter function active during “key off” in automotive application.
    • Count updates every 180° of magnet rotation
    • Tracks magnet rotations in CW/CCW direction from –512 to +511 counts
    • Low power mode (100 µA per die)

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check Stock
ASEK-1331-SUBKIT-T DEMO BOARD -20°C to 85°C No -- Discontinued Contact your
local sales rep
Distributor Stock
ASEK-1331-T-KIT DEMO BOARD -20°C to 85°C No -- Discontinued Contact your
local sales rep
Distributor Stock
A1331LLETR-DD-T 24-lead TSSOP -40°C to 150°C Yes View Data Discontinued 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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