A3144 Digital Unipolar Hall-effect Sensor TO-92

A3144 Digital Unipolar Hall-effect Sensor TO-92 is a reliable, three-terminal device specifically designed to operate with a single magnetic pole to detect position, speed, or current. Utilizing the Hall effect principle, this sensor contains a voltage regulator, a Hall voltage generator, a small-signal amplifier, a Schmitt trigger, and an output transistor, all integrated onto a single silicon chip. Consequently, it provides a stable and predictable digital output (either ON or OFF) whenever it detects a magnetic field strength above a predetermined operate point (B_OP). Furthermore, its unipolar nature means it activates only when presented with the correct magnetic polarity, offering simplified control logic for many applications. Therefore, designers frequently select the A3144 TO-92 package for robust, non-contact sensing solutions across various commercial and industrial environments.

Key Features:

• Digital Unipolar Switching: The sensor switches its output ON (low) when a sufficient magnetic field (South pole facing the marked side) is present, and OFF (high impedance) when the field removes itself.
• Internal Schmitt Trigger: Built-in hysteresis prevents output oscillation (chattering) near the switching point, ensuring clean, sharp transitions between the ON and OFF states.
• Open-Collector Output: The output transistor (NPN) sinks current to ground when active; consequently, this configuration requires a pull-up resistor for logic-level interfacing.
• Wide Operating Voltage Range: The integrated voltage regulator allows the device to operate reliably across a supply voltage range of 4.5 V to 24 V DC.
• Temperature Stability: You can count on the circuit design to compensate for temperature variations, which ensures reliable switching characteristics across the full operating temperature range.

Technical Specifications:

• Supply Voltage (V_CC): 4.5 V to 24 V DC
• Output Current (I_OUT): 25 mA maximum (Sink)
• Operate Point (B_OP): Typical 55 Gauss (5.5 mT)
• Release Point (B_RP): Typical 30 Gauss (3.0 mT)
• Hysteresis ($\Delta$B): 25 Gauss maximum
• Switching Type: Unipolar (Responds to one magnetic pole)
• Operating Temperature Range: −20°C to +85°C (Commercial)

Mechanical Specifications:

• Package Style: TO-92 (Radial, Through-Hole, Transistor-Style Package)
• Pin Count: 3
• Component Material: Silicon integrated circuit encapsulated in plastic.
• Sensing Orientation: The Hall element aligns parallel to the marked face of the TO-92 package.

Dimensions:

• Body Height: ≈ 4.5 mm (excluding pins)
• Body Width: ≈ 4.0 mm
• Lead Spacing (Pitch): 1.27 mm nominal (Half of 2.54 mm standard)
• Lead Material: Tinned Copper
• Weight: ≈ 0.2 g (Extremely small and lightweight)

Pinout and Wiring:

• Pin 1 (V_CC): Connect the positive voltage supply (4.5 V to 24 V DC) here.
• Pin 2 (GND): Connect to the circuit ground (0 V).
• Pin 3 (Output): Connect to the microcontroller input or load via a pull-up resistor (typically 1 kΩ to 10 kΩ) to V_CC.
• Wiring Note: Always place a decoupling capacitor (e.g., 0.1 µF) as close as possible between the V_CC (Pin 1) and GND (Pin 2) pins to ensure stable operation.

Datasheet Reference:

• Download A3144 Hall-Effect Switch Datasheet

Commonly Used in:

• Motor Commutation: Sensing rotor position in brush-less DC (BLDC) motors.
• Proximity Sensing: Detecting the presence or absence of nearby objects using a permanent magnet.
• Security Systems: Serving as the magnetic switch component in door and window alarms.

Applications:

• Speed Measurement: You can build simple tachometers by sensing passing magnetic elements on a rotating shaft.
• Position Detection: Accurately indicating the limit or home position in linear actuators and mechanical assemblies.
• Flow Metering: Sensing the rotation of a magnetic impeller in liquid or gas flow meters.
• Keyboard Encoders: Detecting key presses in some high-reliability mechanical keyboards.

Equivalent Models:

• SS441A (Honeywell): A functionally similar unipolar Hall-effect sensor with a comparable B_OP.
• OH3144: A common cross-reference part number for the A3144, often manufactured by other suppliers with identical specifications.
• US1881: However, note that this is a latching Hall sensor, but it is sometimes used as an alternative when a latching function is acceptable.

Package Includes:

• 1 x A3144 Digital Unipolar Hall-effect Sensor (TO-92 Package)