Hall-effect sensors measure angles in rotating systems

November 19, 2014 // By Christoph Hammerschmidt
Sensors for electronic power steering (EPS) need to provide precise 360° angle readings at high reliability. Allegro Microsystems Europe has developed the A1332 and A1334 angle sensor ICs. Utilising the circular vertical Hall (CVH) technology, these SoCs offer high output refresh rates and low signal-path latency. Besides EPS, these devices are also suited for transmission systems, sensing motor position, throttle position and other parameters requiring precise measurement of angles.

The A1332, with an onboard 32-bit processor and EEPROM for factory and customer programmability, includes segmented and Fourier linearisation functions to support challenging off-axis/side-shaft magnetic sensing configurations commonly found in electronic power steering and transmission applications. The A1332 also supports on-axis/end-of-shaft magnetic sensing configurations, and can produce high-accuracy angle measurements with an output refresh period of 32 µs. The device incorporates a 2-wire I²C digital interface with signal path and I/O diagnostics for achieving higher reliability to meet ASIL automotive safety requirements.

The A1334 has onboard digital signal processing functions and also offers EEPROM for programmability, is designed specifically for on-axis/end-of-shaft applications that require ultra-fast output refresh rates and low signal path latency. Its 4-wire 10 MHz SPI interface offers a 25 µs output refresh period and a nominal signal-path latency of only 60 µs. In addition, the A1334 can operate directly off a vehicle battery, supporting a wide 4.5-14.5 V supply voltage range, while consuming just 10 mA (max) of supply current. Like the A1332, the A1334 includes signal-path and I/O diagnostics for achieving ASIL safety requirements.

Both devices can operate in a low RPM mode, to support up to 12 bits of output resolution in lower angular velocity applications, and in a high RPM mode to support situations demanding faster refresh rates and lower single-path latency.

As part of their signal processing functions, the ICs include automotive-grade temperature compensation to provide accurate angle measurements over the full operating temperature and voltage range of the devices. The A1332 and A1334 are also air-gap independent and can operate over a 300-1000 Gs magnetic target field level, making them less sensitive to stray fields and ensuring high levels of accuracy. The on-chip EEPROM technology also enables flexible programming of end-of-line calibration parameters.

The A1332 and A1334 operate over the -40° to +85°C and -40° to +150°C temperature ranges, respectively, and are each available as a single die in a 1 mm