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SiP format magnetic position sensors ensure car safety

28 Apr 2016

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Ams AG has expanded its portfolio in automotive safety compliant sensors with the introduction of its first magnetic position sensors fully developed using the automotive industry's programme for ISO26262 safety compliance. The product release also includes the company's first magnetic position sensor in a System-in-Package (SiP) format, a space savings package, that enables lower system costs and the placement of the sensor device in environments, that are prohibitive to PCB based packages.

The AS5170 and AS5171 sensors were developed as SEooC (Safety Element out of Context) devices, as defined in the ISO26262 functional safety standard. Consistent with Ams' strategy of helping its customers meet the ever-increasing demand for automotive safety features built into critical vehicle systems, the AS517x parts are Ams' first magnetic position sensors to provide full data path diagnostics, enabling automotive system OEMs to achieve a higher level of ISO26262 system-level compliance.

The diagnostic system built into the AS517x series tests the entire device, from the Hall sensor front end, through the DSP engine which converts raw measurements of magnetic field strength into sine and cosine vectors, to the back-end interfaces and pins.

The AS517x series of sensors, which are qualified to AEC-Q100 Grade 0, very accurately measure the absolute angle of rotation, stated the company. Their high 12bit output resolution enables precise measurements, even for reduced angular excursions down to a minimum arc of 90°. This means, that the devices are geared for a range of safety-critical automotive applications including chassis height, gear shifters, electronic power steering, exhaust gas recirculation and brake pedal as well as throttle position sensing.

The AS5171 comes in an SiP format, which integrates the sensor die and capacitors in a single, encapsulated three-pin package. The SiP offers improved ESD and EMC performance, as well as enhanced supply protection. The supply and output pins are protected against over-voltages up to 20V. The Supply pin also offers -20V of protection against reverse polarity.

The SiP eliminates the requirement to mount a position sensor IC on a PCB, thus reducing component count and system cost, and making for easier design and assembly into the end product.

PA AS5170A block diagram

Figure 1: PA AS5170A block diagram

The AS5171A provides an analogue output, and the AS5171B provides a digital output, which may be programmed either as a PWM interface or as a SENT-compliant interface. The analogue AS5170A and digital AS5170B ICs are housed in an 8-pin SOIC package.

Like every other magnetic position sensor from Ams, the AS5170 and AS5171 benefit from stray magnetic field immunity, enabling unimpaired operation even in the presence of strong magnetic fields generated by electric motors, high current-carrying cables and other external devices.

This results in highly reliable performance and reduces system cost since there is no need for the shielding required by other magnetic position sensors.

The high sensitivity of the Hall sensor front-end in the AS517x devices enables the use of small, low cost target magnets and supports a wide magnetic field strength input range of 5mT to 90mT.

The AS5170 and AS5171 magnetic position sensors are available immediately in production volumes. Unit pricing is $2.64 (AS5170) and $2.87 (AS5171) in order quantities of 1,000.

Evaluation boards for the AS5170 and AS5171 are available from the ams ICdirect online store.

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