1. Sensor Overview & Key Features

️· Type: Hall-effect sensor designed for gear-tooth sensing.
️· Self-Calibrating: A crucial feature. It automatically compensates for installation inaccuracies at power-on. This means performance is more consistent even with varying air gaps.
️· Applications: Primarily for automotive (transmission) and other applications requiring precise gear-tooth detection.
️· High Accuracy: Designed for consistent and accurate performance over a wide range of air gaps and temperatures.

2. Operating & Performance Characteristics

️· Air Gap: Installation inaccuracies are calibrated out at power on.
️· Duty Cycle Maintenance: Maintains accurate duty cycle even with air gap changes, requiring re-powering for significant air gap variations.
️· Target Size/Diameter:
- For best performance with fine-pitch gears (less than 4mm pitch), rotate the sensor face.
- Larger gear diameters (greater than 100mm) improve timing accuracy.
️· Signal Timing Accuracy: Generally better with valley-to-tooth transitions.

3. Operational Considerations and Setup

️· Evaluation Technique: Requires power cycling after changing air gaps to allow for recalibration.
️· Power Supply:
- Unregulated Supply: Requires protection circuitry (Zener diode, resistor, capacitor) to handle transients (load dumps, reverse battery).
- Regulated Supply: Less stringent requirements; basic RC filtering recommended.
️· Repowering: Large air gap changes will require the part to be reset (by cycling power) to maintain the correct duty cycle.

4. Electrical Protection (Unregulated Supply)

️· Overvoltage Protection: Uses a Zener diode and series resistor to limit voltage and current.
️· Reverse Battery Protection: Diode protects the Zener diode.

5. Qualification Testing

️· Rigorous qualification testing is performed before release.
️· Key tests include Temperature Humidity Bias Life, Bake Life, Autoclave, and Temperature Cycling.

6. Important Diagrams/Charts/Figures:

️· Dwg. MH-018-5: Shows target face width and sensor rotation requirements (likely relates to fine pitch gears).
️· Diagrams related to power supply configurations for unregulated and regulated supplies.



Where to Find More Information:

️· Allegro MicroSystems Website: [www.allegromicro.com](http://www.allegromicro.com)
️· "Hall Effect IC Applications Guide" (AMS-702)
️· Application Note 27701