Electronic Design

Dual-Channel Quadrature Bipolar Switch Tackles Tough Environments

Surrey, England: A novel ultra-sensitive dual-channel quadrature Hall-effect bipolar switch IC is designed for rotating ring-magnet based speed and direction sensing applications in harsh automotive and industrial environments.  

The A1230, developed by Allegro MicroSystems Europe, is a temperature-stable magnetic sensing device incorporating two Hall-effect sensing elements spaced 1mm apart. Each element provides a separate digital output for speed and direction signal processing. The digital outputs are out of phase. Thus, the outputs are in quadrature when interfaced with the proper ring-magnet design, allowing easy processing of the speed and direction signals.  

The two Hall elements are photolithographically aligned to better than 1µm—an accuracy the company claims has not been achieved in fine-pitch detection applications. Extremely low-drift amplifiers guarantee symmetry between the switches to maintain signal quadrature.

Allegro’s patented, high-frequency, chopper-stabilisation technique cancels offsets in each channel, providing stable operation over the full specified temperature and voltage ranges. 

The high-frequency chopping circuits also allow for an increased analogue signal-to-noise ratio at the input of the digital comparators within the IC. As a result, the A1230 achieves high digital output jitter performance, which is critical in high-performance motor commutation applications. Thanks to an on-chip low-dropout (LDO) regulator, the A1230 can be used over a wide operating voltage range. Post-assembly factory programming at Allegro provides sensitive switchpoints that are symmetrical between the two switches.

The switch IC features integrated electrostatic discharge protection between outputs and supply voltage to ground, a robust structure for EMC protection, and reverse battery protection on supply and both output pins. 

The A1230 comes in a plastic 8-pin SOIC surface-mount package (L) and a plastic 4-pin SIP (K). Both are available in a temperature range of -40°C to +150°C. Each package is lead-free, with 100% matt tin-plated leadframe.


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