How do I start selecting an Allegro magnetic sensor?

Estimate the magnetic field at the sensor from your magnet and air gap, then choose the sensitivity that keeps the output in range and gives a good signal. Confirm the package, the supply and the temperature range. Those decisions narrow the selection quickly.

How do I choose the sensitivity?

Choose 5.0 mV/G (A1324) for a small field and a short gap, 3.125 mV/G (A1325) for a medium field and 2.5 mV/G (A1326) for a large field. The goal is the largest output that still stays in range at the maximum field. Our FAE team can help size the magnetic circuit.

SIP or SOT-23 package?

The 3-pin SIP is easy to prototype with and fits a through-hole board, and the 3-pin SOT-23 suits a compact surface-mount production board. The electrical performance is the same, so the choice is mechanical. Our FAE team can help match the package to the board.

How do I keep the reading accurate?

Keep the air gap consistent, use a magnet with a stable temperature coefficient, keep the supply clean and keep the sensor away from stray fields. The device cancels its own offset, so the magnetic circuit is the main variable. Our FAE team can review the accuracy budget.

How do I start selecting an Allegro current sensor?

Set the current range just above your maximum current, then choose the sensitivity that gives the resolution you need. Confirm the isolation, the supply and the package. Those decisions narrow the selection quickly.

Which current range should I choose?

Choose the smallest range that covers your maximum current, because a lower range has a higher sensitivity and a better resolution. The 5 A, 20 A and 30 A versions share a package, so you can refine the range later. Our FAE team can match the range to the load.

Why does isolation matter?

The 2.4 kVRMS isolation separates the current path from the signal path, so a high-side or high-voltage measurement is safe and the logic is protected. It removes the need for an isolation amplifier and simplifies the design. Our FAE team can review the isolation layout.

How accurate is the measurement?

The family gives a total output error of about 1.5 percent at 25 °C with a low offset and a nearly zero magnetic hysteresis, and the chopper-stabilized circuit keeps the accuracy stable. Calibrate the offset and the gain for a demanding design. Our FAE team can review the accuracy budget.

How do I design the magnetic circuit?

Choose a magnet and an air gap that give a smooth, monotonic field across the travel range, and fix the gap with a mechanical stop so the reading repeats. Model or measure the field, then choose the sensitivity to match. Our FAE team can review the magnetic circuit.

How do I keep the output low-noise?

Keep the supply clean with a bypass capacitor across the supply pins, keep the output trace short and away from switching nodes and keep the sensor away from stray magnetic fields. The device already cancels its own offset and low-frequency noise. Our FAE team can review the layout.

How do I measure an angle?

Place the magnet so the field rotates with the shaft and use two sensors in quadrature, or a single sensor on a rotating field, and take the arctangent of the two signals. The field should vary smoothly and sinusoidally with the angle. Our FAE team can help with the geometry.

How do I improve temperature stability?

Use a magnet with a stable temperature coefficient, keep the air gap fixed and rely on the device's temperature-stable sensitivity and offset cancellation. Confirm the accuracy across the full temperature range on the bench. Our FAE team can check the over-temperature budget.

The motor will not turn. Where do I start?

Check the supply voltage against the range, the logic and the enable pins, the current-limit setting and the step and direction signals. A driver that is disabled, a current limit set too low or a missing logic supply keeps the motor still. Measure the supply and the logic during start-up.

The driver runs hot. What should I check?

Check the output current against the rating, the exposed-pad soldering and the copper area, and the ambient and airflow. The dissipation scales with the current squared and the on-resistance, so a poor thermal path or a high current limit raises the temperature. Improve the thermal path and confirm the current limit.

The current limit does not work. What is wrong?

Check the sense resistor value and the reference voltage, and confirm the PWM decay mode and the off-time. A wrong sense resistor or a mis-set reference gives the wrong limit, and the decay mode affects the ripple and the average current. Our FAE team can review the current-limit setting.

The driver trips its protection. What should I check?

Check for a motor short to ground or to the supply, an over-current from a stall or an inrush, and an over-temperature. The driver flags over-current, short, under-voltage and thermal faults, so trace which one is active and fix the cause. Our FAE team can help diagnose the fault.

What is the standout feature of the Allegro range?

The standout feature is the depth of the Hall-effect sensing portfolio combined with integrated motor drivers, so one supplier can provide the position sensor, the current sensor and the driver for a complete motion system, all with stable accuracy and integrated protection. The main design care points are the magnetic circuit and the thermal design.

How do the linear Hall sensors perform in practice?

In practice the A1324/5/6 family gives a low-noise, temperature-stable output that is easy to interface, and the ratiometric output simplifies the ADC. On the bench the sensitivity and the offset held their specification when the supply was kept clean. Confirm the magnetic circuit and the air gap.

How do the current sensors compare to a shunt?

An ACS712 current sensor measures the current without a shunt and with 2.4 kVRMS isolation in one package, so it removes the shunt, the amplifier and the isolation amplifier, and the insertion loss is low. It is a clean solution for a high-side or a motor current measurement. Our FAE team can compare the options for your design.

Can I get samples to evaluate?

Yes. We provide samples of the Allegro sensors and drivers for your own testing, with documentation included and FAE support during bring-up. Request a sample and we will confirm stock and lead time.

Technical Support | Allegro Expertise | BeiLuo

Guides, application notes, troubleshooting and reviews from BeiLuo's FAE team covering Allegro magnetic sensors, current sensors and motor drivers in detail.

Guides 2 Application Notes 1 Troubleshooting 1 Reviews 1

How to Select an Allegro Magnetic Sensor

2026-07-26 - Guides - By Wei Ming Chen

Compare Allegro linear Hall-effect sensor ICs by sensitivity, package, supply and temperature for accurate position, angle and proximity sensing in one part.

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How to Select an Allegro Current Sensor

2026-07-21 - Guides - By Hao Jun Li

A practical method for selecting Allegro isolated Hall-effect current sensor ICs by range, sensitivity and isolation for motor control and supply rails.

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Allegro Hall-Effect Sensor Design Notes

2026-07-16 - Application Notes - By Jing Wen Zhao

Magnet, air-gap, supply and layout guidance for applying Allegro linear Hall-effect sensor ICs reliably in position, angle and current measurement systems.

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Troubleshooting Allegro Motor Driver Designs

2026-07-09 - Troubleshooting - By Hao Jun Li

A systematic method for diagnosing start-up, current-limit, thermal, step and protection faults in Allegro stepper and DC motor driver designs on the bench.

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Allegro Sensor and Motor Driver Review

2026-06-30 - Reviews - By Wei Ming Chen

A hands-on review of Allegro magnetic sensors, current sensors and motor drivers for motion and sensing designs, covering accuracy and range over temperature.

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Meet Our FAE Team

Wei Ming Chen

Senior FAE Engineer, Magnetic Sensors

Magnetic SensorsPosition SensingMotor Control

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Hao Jun Li

FAE Engineer, Sensing and Drivers

Current SensingMotor DriversThermal

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Jing Wen Zhao

FAE Engineer, Applications

Hall-Effect SensingAccuracyReliability

Author profile