The Importance of the ISO 26262 Automotive Safety Standard: New Sensors from ams

In this News Brief, we take a look at ams AS5270 position sensors, which are ISO 26262 compliant.

ams recently announced the AS5270 position sensors as the newest addition to their magnetic position sensors portfolio. In order to assist automotive OEMs with high safety standards, the AS5270A and AS7270B SoC devices have dual-die redundancy, full data path diagnostics, and self-test capabilities. 

 

The AS5270 position sensors are created for automotive applications. Image courtesy of ams.

 

Per the ISO 26262 functional safety standard specification, the AS5270A/B SoC devices were developed as Safety Element out of Context (SEooC) devices.

The ISO 26262 Functional Safety Standard

The ISO 26262 Functional Safety Standard (PDF) is an extension of IEC 61508 functional safety of electronic safety-related systems. The IEC was created for use with large industrial, safety-critical systems. With these larger systems, installation is one of the most critical aspects of safety. Because automotive embedded systems are commonly sold as OEM products, a different safety standard was created.

ISO 26262 sets Automotive Safety Integrity Levels (ASILs) for manufacturers of the electronic systems in automobiles. ASILs involve an extended hazard analysis and risk assessment built on three variables: severity, probability of exposure, and controllability.

Severity evaluation can range in four classes from “no injuries” to life-threatening injuries” and looks at potential hazards and injuries a product could cause to the driver, passengers, or surrounding drivers. Once severity is determined, the probability of exposure can be set. Probability of exposure has a range of five classes, from “incredible” (as in, unlikely) to “high probability”. Controllability refers to the control the driver has over the car and has four classes ranging from “controllable in general” to "difficult to control or uncontrollable”.

The AS5270 Family

The AS5270A provides an analog output interface and the AS5270B provides a digital interface and can be programmed as SENT-compliant or PWM output interface. Both options are based on Hall sensor technology.

 

Block diagrams for the AS5270A and AS5270B. Image courtesy of ams.

 

Applications for the AS5270 include brake and gas pedals, throttle valve and tumble flaps, steering angle sensors, chassis ride, EGR, fuel-level measurement systems, 2/4WD switch, and contactless potentiometers.

According to its datasheet (downloadable here), "The AS5270A provides an analog output interface and the AS5270B provides a digital interface and can be programmed as SENT-compliant or PWM output interface." It's worth noting that these are one-time programmable chips and that both are based on Hall sensor technology.

One of the most important features of automotive systems is, obviously, safety. Manufacturers and designers aim for any part to have as few defects as possible but automotive applications are unique in that they're widespread and have stringent standards (like ISO 26262). The AS5270 family partly addresses these safety issues with redundancy. The AS5270A accomplishes this partly by stacking two chips. By using separate pins for the two chips, meaning that, if one should fail due to electrical faults, it won't take its partner chip with it.

 

Features

• 12-bit resolution @90° minimum arc
• Low output noise, low inherent INL
• Magnetic stray field immunity
• Functional safety, diagnostics, dual redundant chip version
• AEC-Q100 Grade 0 qualified