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Datasheets:
A3250 and A3251: Field Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches (PDF)
Selection Guides:
Hall-Effect Sensor ICs,
Unipolar Hall-Effect Digital Switches
Technical Publications:
Programmable Boards Adjustment (PDF),
Programming a Back Biased Switch for Proximity Sensing / Proximity Sensing Programming Technique,
Unipolar Hall-Effect Sensor IC Basics
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Allegro MicroSystems, Inc. Offers the First Programmable Unipolar Hall-Effect Switch
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ASEK-02 Sensor IC Evaluation Kit,
Allegro Sensor Evaluation Kit Technical Guide
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A3250 and A3251
Field Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches
Features
- Chopper stabilization for stable switchpoints throughout operating temperature range
- Externally programmable operate point (through VCC pin)
- On-board voltage regulator for 4.2 to 24 V operation
- On-chip protection against:
- Supply transients
- Output short-circuits
- Reverse-battery condition
Description
The A3250 and A3251 are field-programmable, chopper-stabilized, unipolar Hall-effect switches designed for use in high-temperature applications. These devices use a chopper-stabilization technique to eliminate offset inherent in single-element devices.
The A3250 and A3251 are externally programmable devices. The devices have a wide range of programmability of the magnetic operate point (BOP) while the hysteresis remains fixed. This advanced feature allows for optimization of the sensor switchpoint and can drastically reduce the effects of variations found in a production environment, such as magnet and device placement tolerances.
These devices provide on-chip transient protection. A Zener clamp on the power supply protects against overvoltage conditions on the supply line. These devices also include short-circuit protection on the output.
The output of the A3250 switches LOW when subjected to a south-polarity magnetic field with a flux density that exceeds the threshold for BOP, and switches HIGH when the field drops below the magnetic release point, BRP. The output of the A3251 has the opposite polarity, switching HIGH in a south-polarity magnetic field that BOP, and switching LOW when the field drops below BRP.
The other differences in the devices are the power-on state. The A3250 powers-on in the HIGH state, while the A3251 powers-on in the LOW state.
Three 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 (suffix, –T).
Functional Block Diagram
| Part Number | Package Type | RoHS Compliant |
Part Composition/ RoHS Data |
Temperature | Comments | Samples | Distributor Stock |
|---|---|---|---|---|---|---|---|
| A3250LLTTR-T | 3-lead SOT | Yes | view data | -40 °C to 150 °C |
Contact Local Sales Representative or check distributor stock |
Allegro's products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system.