Quality Standards and Environmental Certifications

Increasing System Safety using the A1365 Programmable Linear Hall-Effect Sensor IC with Self-Test Diagnostic Mode

Increasing System Safety using the A1365 Programmable Linear Hall-Effect Sensor IC with Self-Test Diagnostic Mode

By Wade Bussing, Applications Engineer,
亚博棋牌游戏Allegro Microsystems，LLC

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Abstract

此应用笔记提供了实现自检诊断模式的指南A1365from Allegro MicroSystems in order to verify system functionality and safety in the application. To learn more about the A1365 from Allegro MicroSystems, refer to the device’s datasheet at www.wangzuanquan.com.

Introduction

汽车安全水平的出现刺激了安全要求的增加，使IC和传感器安全功能与某些应用中的目标性能规格一样重要。亚博尊贵会员随着安全目标乘以整个系统设计过程，客户需求可用于诊断系统中异常的智能传感器。A1365的内置自检模式授予用户此类洞察力。

The Self-Test mode on the A1365 covers the entire signal path, from the analog output (VOUT) andFAULT将引脚输出到与霍尔换能器的连接。请参阅图1中A1365的框图，突出了绿色片上芯片测试电压的注入点。

The A1365’s Self-Test mode allows the user to verify, at any point, connectivity of the analog signal path, drifts in quiescent output voltage, as well as connectivity and functionality of the Over Field Fault signal path. By comparing the voltages and various timings measured during the Self-Test mode, the user can also evaluate the integrity of any external devices, including system ADCs and overcurrent fault control devices. The Self-Test Fault feature simplifies end-of-line verification of overcurrent fault circuitry external to the A1365 without the burden of injecting large full-scale
电流。

The Self-Test mode is intended to reveal gross single point failures in the Hall path, but does not test the sensitivity of the Hall transducer itself.

Figure 1: A1365 Functional Block Diagram
Figure 1: A1365 Functional Block Diagram

Enabling the Self-Test Mode

The Self Test feature is disabled in all sales versions of the A1365 IC. However, the test mode is easy to enable using the Allegro A1365 Samples Programmer and an ASEK evaluation board. The A1365 Samples Programmer is available on Allegro’s software portal athttps://registration.allegromicro.com.有关收购ASEK评估套件的信息，请联系您的销售代表。

在A1365上启用自检模式，通过按“开机”按钮上电 - 设备上电[1]on the A1365 Samples Programmer shown in Figure 2. Confirm that the device is operational
by verifying VCC., ICC.并且使用“更新”按钮按预期读取输出值[2]。

图2：A1365样品程序员的电源面板
图2：A1365样品程序员的电源面板

The “Memory” panel on the programmer displays all available registers on the A1365 device, along with a brief description of each register’s function[3]。有关更多信息，请参阅图3。
图3：来自A1365样本程序员的存储面板
图3：来自的内存面板
A1365样品程序员

Choose the “Select All” button[4]，followed by the “Read Selected” button[5]，which will read back the memory contents of the device and populate the code and value columns with the returned data. Prior to making any changes to the device’s memory, it is best practice to save a local copy of the EEPROM contents to revert back to. Choose the “Save” button[6]to generate either a .csv or .txt file for safekeeping.

使自测模式,裁判er to Figure 4. Scroll down to the field “ST_DIS” (self-test disable)[7],选择“取消选择”按钮[8]，然后仅使用复选框选择“ST_DIS”字段。通过将“0”在单元格中将“ST_DIS”代码列设置为“0”，或选择“零选择”按钮[9]在GUI上。准备就绪后，按“写入所选”按钮[10]将新值写入\ EEPROM。最好读回相同的寄存器以验证更改。选择“读取选定”[11]确认“ST_DIS”位已被清除。自检模式现在已启用。

图4：自检启用A1365样品程序员
图4：自检启用
A1365样品程序员

Initiating the Self-Test Mode

Once enabled, the Self-Test mode may be initiated by pulling the A1365’sFAULT别针低。该设备立即不进入自检模式;这FAULTpin must be held low for a time period greater than the “Self-Test Start Time” to enter the Self-Test diagnostic mode. The Self-Test Start Time is programmable and is designated in the programming field “ST_START_TIME”. There are sixteen codes which correspond to twelve discrete Start Time values.

The available codes for Self-Test Start Time and their corresponding time delays are listed in Table 1.
Fig
自检开始时间由何时定义FAULTpin voltage (VFAULT）低于自测阈值电压（VStth.）在传感器进入自检模式之前。传感器通过将模拟输出驱动到自检低压（V.STL.). If at any point during Self-Test Start Time the sensor detects a magnetic input exceeding the programmed fault threshold, the Self-Test timer will reset.

图5中的曲线显示了v的时间OUTto reach VSTL.之后FAULT针对A1365上的所有自动测试开始时间代码被拉低。

图5：所有代码的自检开始时间
图5：所有代码的自检开始时间

Self-Test Fault Request Time

自检故障请求模式允许用户验证A1365上的UserProgramMed故障阈值。设备将在后面进入自检故障模式FAULTPIN释放的时间比自检故障请求时间长（ST_FR_TIME）。

在释放引脚后，但在自检故障请求时间到期之前，输出被驱动到自测高压（V.st). As the device enters Self-Test Fault Request Mode, the output of the
device is driven to saturation (V坐（高）).

The available codes for Self-Test Fault Request Time (ST_FR_TIME) and their corresponding delays are listed in Table 2.
Fig
在自检故障模式中，A1365将驱动VOUT饱和度，都是v坐了（h）and V坐（l）。当V.OUT通过用户编程的故障阈值（FLT_Thresh），传感器的故障引脚将断言表示故障情况。请注意，如果启用钳位，此模式会暂时禁用钳位。

Self-Test Fault Pulse Width Time

A1365将驾驶并保持vOUT每个测试电压都是由自检故障脉冲宽度时间（st_fpw_time）定义的周期。表3列出了自检故障脉冲宽度时间及其相应的脉冲宽度时间的可用码。

Fig

完整的自检模式序列

整个自检模式序列如图6所示。自测试模式期间的施加的磁场必须为零。

Figure 6: Self-Test Mode Sequence
Figure 6: Self-Test Mode Sequence
For the case in Figure 6, ST_START_TIME = 50 ms, ST_FR_TIME = 10 ms, and ST_FPW_TIME = 10 ms. The Self-Test and Magnetic Fault settings are shown in Figure 7.
图7：图6中序列的自检和故障设置
图7：自检和故障设置
对于图6中的序列

The Self-Test sequence is described in the list below. Each step corresponds to a point in time on the plot in Figure 7.

  1. The A1365’sFAULTpin is pulled low externally to initiate the Self-Test mode. The A1365 would still properly respond to magnetic fields at this time.
  2. 在ST_START_ TIME和DRIVE V之后，该设备进入自测感测模式OUTto VSTL.。
  3. V.OUTremains at VSTL.until theFAULTPIN被释放。
  4. V.OUTis driven to Vstfor the duration of Self-Test Fault Request Time, ST_FR_TIME.
  5. The device enters Self-Test Fault Request mode and VOUTis driven to V坐了（h）for ST_FPW_TIME and theFAULTpin is asserted.
  6. V.OUTis driven to QVO for ST_FPW_TIME (10 ms) and theFAULTpin resets.
  7. V.OUTis driven to V坐（l）for ST_FPW_TIME (10 ms) and theFAULTpin is asserted.
  8. 自检序列已完成，设备返回正常操作（任务模式）。

申请案例

The Self-Test mode on the A1365 may be used to verify gross anomalies and single point failures on the A1365 device. This feature may also be used to confirm the integrity and timing of other system devices, including ADCs and fault control circuitry.

The application schematic in Figure 8 shows such a system. The A1365 is installed in the gap of a laminated core and is used to sense magnetic field generated by current flow in a conductor. The analog output, VOUT, is connected to an ADC while theFAULT引脚连接到微控制器上的通用I / O引脚。假设I / O连接FAULTpin signals a system interrupt in the event of an overcurrent condition. This interrupt prompts the microcontroller to put the system in a safe state by disconnecting current flow in the conductor.

图8：应用原理图与A1365，ADC和过电流故障控制
图8：应用原理图与A1365，ADC和过电流故障控制

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本文档中包含的信息也没有t constitute any representation, warranty, assurance, guaranty, or inducement by Allegro to the customer with respect to the subject matter of this document. The information being provided does not guarantee that a process based on this information will be reliable, or that Allegro has explored all of the possible failure modes. It is the customer’s responsibility to do sufficient qualification testing of the final product to insure that it is reliable and meets all design requirements.