PCB-less 3D magnetic sensor for safety and ADAS applications

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By Christoph Hammerschmidt

With the A31316 Hall-effect position sensor, Allegro MicroSystems has further extended its 3DMAG line of 3D sensors. Offered in an industry-smallest 4 × 4 mm body PCB-less package, this sensor is said to be ideal for automotive safety and advanced driver assistance systems (ADAS) applications that require high levels of flexibility, reliability and performance in harsh conditions such as powertrain and chassis applications, as well as industrial applications that require linear or rotary sensing.

Powertrain and chassis applications, passenger restraint systems, and shifter systems, are subjected to environmental vibrations and contaminants that can degrade performance. The position sensors used in powertrain and chassis applications typically require support components, like PCBs and capacitors, and—when a position sensor is required in a dirty, high-vibration environment—the assembly of system components can become corrupted by debris and vibration, which can inhibit the performance of the assembly. The same is true for many industrial linear and rotary sensing applications. Designers are challenged to fit robust designs within the allotted dirty, high-vibration space.

The A31316 3D Hall sensor eliminates the need for a PCB or other external components. This sensor integrates the die and capacitors in a single package to address the need for high-performance, compact position sensors that are robust to these environments. For vibration-robust designs, the A31316 pins can be welded or soldered directly to connector leadframes and can be overmolded or potted for a tight seal. These integration options greatly reduce the ability for contaminants and vibration to affect performance and can bring new design flexibility to spaces where mechanical vibration and contamination are potential issues.

Designed for both rotary and long-stroke linear applications, the A31316 maintains high angle accuracy across the full Grade 0 temperature range (–40°C to 150°C). Its flexible calibration table (33 fixed points or 22 freely placed points) enables options that can reduce the time and complexity of end-of-line calibration and minimise errors due to mechanical misalignment. The A31316 contains advanced on-chip diagnostic features to ensure reliable, safe operation.

The 3DMAG family of rotary and linear magnetic position sensor ICs for automotive and industrial applications combine Allegro’s proven planar and vertical Hall-effect technologies to measure magnetic field components along three axes (X, Y, Z), enabling true 3D sensing capabilities with a wide magnetic dynamic range without saturation. The newest addition to Allegro’s 3DMAG family of magnetic sensors, the A31316, is the company’s first magnetic position sensor to provide multi-direction measurement in a PCB-less SIP package. The A31316 provides designers with a configurable signal path and flexible linearisation for end-of-line calibration to optimise measurement accuracy. The IC can compensate for nonlinear fields and static sensor-to-magnet misalignment errors, and the high degree of configurability makes it easy for designers to optimise for accuracy and calibration time. This helps minimise processing in the electronic control unit (ECU) and maximises end-of-line yield for nonideal magnets and mechanical assembly tolerances. Multi-level output using binning can integrate the functions of multiple magnetic switch ICs into a single A31316.

The A31316 integrates a Manchester interface for programming the EEPROM through the output pin, which eliminates the need for a separate programming interface. It stores factory and customer-programmed calibration settings, with dedicated registers for customer use. The device includes the industry’s fastest SENT protocol with 0.5 µs to 10 µs tick times, and includes a pulse-width modulation (PWM) interface with 125 Hz to 16 kHz carrier for simple digital interface to microcontrollers.

Following Safety Element out of Context (SEooC) functional safety guidelines, the A31316 sensor supports ASIL B system-level integration in accordance with ISO 26262 and is automotive qualified to AEC-Q100 Grade 0.


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