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Hall-Effect-Latches and Bipolar Switches

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Hall-effect latches are most comm in sensing multi-pole ring magnets for motor commutation, because they require a south pole of sufficient strength to turn the output on and a north pole of sufficient strength to turn the output off. These contactless senonly usedsing solutions require few external components and can withstand the hostile operating conditions of automotive applications.

Specific advantages of Allegro’s solutions include:

  • 4× chopper-stabilization for offset cancellation provides: enhanced switch point stability that increases accuracy in measuring motor speed or duty cycle, and industry leading jitter performance that is 2× better than competitor devices
  • Low voltage (3 V) operation and lower ICC for more power efficient devices
  • Certain products (A1225, A1227, A1229) are designed to survive harsh automotive transient conditions, including double battery and 40 V load dump, without a limiting series resistor, eliminating the need for external components and preventing transient voltage field failures

Allegro is a market leader in the area of Hall latches, and has a broad range of part sensitivities for latches that cover any desired magnetic switch points for just about any application requirement.

 

 

Hall-Effect Latches and Bipolar Switches - without Chopperstabilization

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This section includes products developed for very specific application needs.  Please consult with your local Allegro Field Applications Engineer to confirm if one of these products is the best choice for your design.

Continuous-time devices have generally been superseded by chopper-stabilized implementations.  However, there are a few specialized applications where continuous-time switches or latches might be appropriate:

  • Applications where the sensor is power-managed by switching its power supply on and off, as continuous-time devices have faster wake-up times
  • High-speed applications that demand the absolute lowest jitter or best repeatability, as there is no jitter produced by the action of the multiphase chopping

Allegro is a market leader in the area of Hall latches, and has a broad range of part sensitivities for latches that cover any desired magnetic switch points for just about any application requirement.

Dual Hall-Effect Latches

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Dual element devices are integrated circuits that contain two independent Hall-effect switches. The digital outputs are out of phase so that the outputs are in quadrature when interfaced with the proper ring magnet design (alternating pole ring magnet). This allows either the user to externally process the output signals to determine speed and direction of an encoder ring magnet or certain devices to internally process these signals and output speed and direction signals. Extremely low-drift amplifiers guarantee symmetry between the switches to maintain signal quadrature. The Allegro patented, high-frequency chopper-stabilization technique cancels offsets in each channel providing stable operation over the full specified temperature and voltage ranges.

The high-frequency chopping circuits allow an increased analog signal-to-noise ratio at the input of the digital comparators internal to the IC. As a result, the A1230 achieves industry-leading digital output jitter performance that is critical in high performance motor commutation applications.

Magnetically Actuated Lighting Solutions

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Allegro MicroSystems, LLC offers a wide variety of lighting solutions. By combining industry-leading Hall-effect sensor technology with proven LED driver technology, Allegro offers LED lighting solutions for automotive, industrial, commercial, and consumer applications.

These product complement Allegro’s portfolio of general-purpose LED drivers and includes fully integrated lighting solutions as well as a collection of magnetic digital position sensor ICs that enable system integrators and designers to create custom lighting solutions to meet virtually any requirement.

Allegro’s LED lighting solutions are simple to design and implement with minimal external circuitry while having the capability to address complex lighting needs.

Key features of our magnetically actuated lighting solutions include:

  • Flexibility: Highly sensitive, omnipolar magnetic switches support flexibility in system design and manufacturing and accommodate large air gaps and mechanical misalignment.
  • Elegance: These simple solutions solve complex lighting challenges in minimal space and with minimal design effort, component-count, and cost; LED drivers with adjustable on/off ramp rates (“theater effect”) provide a high-end feel.
  • Reliability: Hall-effect switches are contactless, can be totally sealed, and do not wear out like mechanical switches; these solid-state solutions are stable over temperature and supply voltage.
  • Ruggedness:  Allegro specializes in automotive-grade (AEC-Q100) solutions for harsh environments with features like reverse-battery protection, short-circuit protection, thermal shutdown, and wide operating temperature and voltage ranges.

Micropower Hall-Effect Switches

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Micropower switches are integrated Hall-effect sensor ICs designed specifically for use in battery-operated devices, providing low power consumption for longer battery life. They are typically used for on/off switches (open/close) in cellular flip-phones, PDAs, and laptop computers, or for detecting motion or tampering in utility meters.

During operation (awake mode), these ICs compare the actual magnetic field detected with the internally compensated thresholds and switch the output on in the presence of sufficient magnetic field. During sleep mode, the output stage is latched. Current consumption is significantly reduced by cycling the awake and sleep periods.

The switching behavior of micropower switches is omnipolar, which means they can be switched on with either the North or South pole of a magnet.

Allegro offers unique 3D omnipolar sensor ICs that can detect magnetic fields of either polarity and in any direction. They are highly sensitive, making them ideal for detecting tampering via magnetic fields in applications such as smart meters, ATMs, gambling/gaming machines, ticket machines, electronic locks, etc. They can also be used as highly flexible proximity sensors, as they are insensitive to magnet orientation/direction.

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