Magnetic Sensor ICs Offer Diagnostics for ASIL Compliance - raybet软件,raybet投注,raybet竞猜违法吗

Magnetic Sensor ICs Offer Integrated Diagnostics for ASIL Compliance

By Gary Pepka, Allegro MicroSystems, LLC

Abstract

当前的智能车辆控制革命rol systems relies substantially on the rapidly developing physical detection technology called magnetic sensor integrated circuits (ICs). The complexity, reliability, flexibility, and functionality of these non-contacting, magnetic sensor ICs have all but dispelled the need for electromechanical switches in just about every application in latest generation automobiles. Yet, accompanying this increase in usage of complex electronic devices, is a heightened concern over difficult-todetect, system-level risks. This, in turn, has led the automotive industry to focus on automotive functional safety. The ISO 26262 functional safety standard outlines a development process including predictive analysis to minimize risk. This process, in turn, requires advanced diagnostics capabilities integrated directly into magnetic sensor IC systems. An examination is made of a new type of magnetic sensor IC that implements integrated diagnostics, using an innovative embedded solid state coil for end to end system test.

概述

打开任何最新型号的汽车的门，你马上就会被一个看不见的电子传感器网络所包围。它们检测安全带屈曲、车窗或天窗夹伤、换档杆位置、发动机变速器转速和方向以及凸轮轴位置，仅举几个应用实例。随着各种非接触式磁探测器（如霍尔效应、巨磁阻、各向异性磁阻）的发展，实时传感在这些应用中的渗透已经成为现实。除了具有非常小的外形尺寸外，这些最先进的固态半导体集成电路还具有成本效益高、功率效率高、非接触式的特点，能够在车辆发动机最恶劣的环境中收集普及的数据流，并对车辆状况的最微小变化作出微妙的响应。雷竞技最新网址

These detection systems provide an advanced level of computing sophistication, providing a high degree of output permutations. This has presented a challenge in achieving functional safety per ISO 26262, because the combination of device state complexity and the almost infinite variety of vehicle operating conditions makes it unlikely that all usage scenarios and failure modes can be anticipated by design or discovered in testing programs. Given that almost instantaneous response may be required to protect passengers and preserve the vehicle, these ingenious detection systems must be able to self-diagnose, and often even correct themselves, when they are functioning improperly.

Traditional solutions use electromechanical switches with limited operational states (operating or not), so failure detection is straightforward. Welded reed switch contacts present a short. Broken switch springs prevent output state change. System level failures are difficult to anticipate. Preventive maintenance is often based on generic Mean Time to Failure (MTTF) data, with switches over-designed to accommodate all reasonable circumstances without adjustment.

Figure 1: Magnetic Hall-effect Based Sensor ICs Provide Compact Data Gathering in Restricted Locations Such as Gear Shifters and Seat Belt Buckles

Figure 1: Magnetic Hall-effect Based Sensor ICs Provide Compact Data Gathering in Restricted Locations Such as Gear Shifters and Seat Belt Buckles

ICs can provide suboptimal outputs, so automotive use requires additional safety measures to avoid unreasonable residual risk according to Automotive Safety Integrity Levels (ASIL), ISO 26262. ASIL assigns safety goals, rather than characterizing entire systems or components. The rigorous ASIL level D requires manufacturers follow strict development guidelines, including Failure Modes Effects and Diagnostics Analysis (FMEDA) to quantify even very low risks of failures. These complexities require comprehensive diagnostics to ensure detection of system level failures and enable safe (limp home) modes.

Redundancy in Safety Critical Applications

For safety critical functions, a feasible option is redundancy in the system. Electromechanical designs are typically bulky and in-line, so they cannot accommodate fail-over redundancy, where alternative controls can be brought on line. Magnetics-based control systems accommodate fail-over redundancy by allowing automatic swapping of control circuits in place, because magnetic sensor ICs do not require contact or direct electrical connection with the mechanical target or electrical circuit being detected.

冗余有多种形式。系统可以包括一对彼此非常接近的非接触式磁性传感器ic。每个传感器IC都有自己的电源、接地和输出，因此如果其中一个发生故障，则在诊断检测到故障后，另一个将接管。互补传感器IC可以简单地用来通知控制器，当它应该切换时，它的队列没有切换。此外，还有能够自我诊断的传感器IC，能够在控制器不能正常工作时通知控制器，而无需额外的传感器IC的帮助。

电磁传感器集成电路中的启用诊断

Magnetic sensor ICs may require monitoring to ensure that the device itself is operating properly and also to ensure switching occurs at the appropriate time with respect to a change in magnetic field.

One approach is to supply a single self-diagnosing sensor IC, which can be less costly, requires less PCB space, and is easier to manufacture in the application than two complementary sensor ICs. This solution also assists design engineers with meeting their targeted functional safety requirements, by addressing the complexity of determining proper electrical performance and magnetic switching.

A recent advancement in self-diagnostics, in particular with the phase involving applied magnetic field analysis, is the use of embedded detector coils on magnetic sensor IC chips. An example is shown in Figure 2, where Hall elements are surrounded by an embedded coil in the雷竞技竞猜下载Allegro MicroSystems A1160单极霍尔效应开关. This provides a cost effective and space saving solution, eliminating the need for external magnetic field conditioning structures to concentrate and guide the ambient magnetic field.

Figure 2: Detection of Magnetic Field Fluctuations

Figure 2: Detection of Magnetic Field Fluctuations

The detection of magnetic field fluctuations is enhanced by an innovative coil structure that surrounds the Hall elements in the Allegro MicroSystems A1160. The coil and Hall elements are embedded in the IC substrate.

The device follows the typical unipolar Hall-effect switch behavior: the device output turns on when the embedded Hall elements sense a perpendicular south polarity magnetic field of sufficient strength to cross the internal comparator switch point. The unique aspect of the device is the on-chip coil embedded in the silicon of the IC. The coil wraps around the Hall elements. When a logic I/O pin, called the Diagnostic Enable pin, is pulled high, the device passes 10 mA of current through the coil. The energized coil generates a field, which, due the close proximity of the coil to the Hall elements, is sufficient to turn on the device and evaluate the entire signal path of the device (including the sensing elements). While the Diagnostic Enable pin is high, the device outputs a pulse width (PW) signal. If the PW signal has a 50% duty cycle, the device is deemed functioning properly. If the PW signal has a 0% or a 100% duty cycle, then the device is deemed functioning improperly (see Figure 3).

图3:Allegro微系统A1160中的自我诊断雷竞技竞猜下载

图3:Allegro微系统A1160中的自我诊断雷竞技竞猜下载

当诊断启用引脚拉高时，设备输出诊断信号。50%的占空比表示工作正常。

To enable self-calibration for these diagnostics, the number of coil turns is fixed and the amount of current is regulated .Therefore, the amount of field generated by the coil is precisely repeatable and if the diagnostic magnetic field changes for some reason (i.e. due to time or stress), the diagnostic mode can detect it. The comparator is the same for both diagnostic mode and normal operation, and what changes is the offset (mV) between diagnostic mode and normal operation (see Figure 4). As a result, when the device is in diagnostics mode, the operation of the diagnostics signal from the regulator to the energized coil and all the way to the output provides an end-to-end test of the full signal path (see Figure 4).

Figure 4: Matched Comparators

Figure 4: Matched Comparators

Matched comparators ensure self-diagnostics mode validates normal mode operation in the Allegro MicroSystems A1160.

为了防止外部磁场移动的附带影响，这种特殊的集成线圈概念提供了由感测元件差分感测线圈的额外好处。这意味着可以随时使用诊断功能，即使设备存在足够强度的外部磁场，以便在正常操作模式下打开设备。此外，由于在诊断模式期间将传感元件重新配置为对差分磁场敏感，因此在传感元件处直接拒绝任何外部磁场。

Additional Applications Being Discovered

This pioneering device design provides modal diagnostics in response to an ECU polling signal, and devices in development also run diagnostics at startup. A typical application circuit for the A1160 is shown in Figure 5, and a variety of output options (2-wire or 3-wire) are being developed, with sensing technologies for position, travel, speed, and direction change. Initially for enhancing the ability to achieve functional safety requirements for the automotive market, applications are limitless, including industrial automation and white goods.

图5：实现磁感应IC解决方案的典型应用

图5：实现磁感应IC解决方案的典型应用.

摘要

The ever-evolving requirements of the automotive, industrial, and commercial markets for increased reliability and functionality will continue to drive demand for electronic content, including non-contact magnetic sensor ICs with diagnostics. The innovative Allegro diagnostic switch with its integrated coil provides design engineers with a unique, cost-effective and user-friendly solution to satisfy almost any safety requirement.

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