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范一样重要。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。

A1365上的自检模式从模拟输出覆盖整个信号路径（V._OUT) and过错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。

A1365的自检模式允许用户在任何时候验证模拟信号路径的连接，在静态输出电压中漂移，以及通过现场故障信号路径的连接性和功能。通过比较自测试模式期间测量的电压和各种定时，用户还可以评估任何外部设备的完整性，包括系统ADC和过电流故障控制设备。自检故障特征简化了A1365外部的过电流故障电路的线路核实，而不会注入大全尺寸
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.

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 V_CC., I_CC.并且使用“更新”按钮按预期读取输出值[2]。

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。

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.

要启用自检模式，请参阅图4.向下滚动到字段“st_dis”（自检禁用）[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]写\ eepm的新值。最好是practice to read back the same register to verify the change. Choose “Read Selected”[11]确认“ST_DIS”位已被清除。自检模式现在已启用。

Initiating the Self-Test Mode

启用后，可以通过拉动A1365来启动自测试模式过错别针低。该设备立即不进入自检模式;这过错pin 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.

自检开始时间由何时定义过错pin voltage (V_过错）低于自测阈值电压（V_Stth.）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 V_STL.之后过错针对A1365上的所有自动测试开始时间代码被拉低。

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过错PIN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）。当设备进入自检故障请求模式时，输出
device is driven to saturation (V_坐（高））。

表2列出了自检故障请求时间（ST_FR_TIME）及其对应延迟的可用码。

在自检故障模式中，A1365将驱动V_OUT饱和度，都是v_{坐了（h）}和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。

自检故障脉冲宽度时间

A1365将驾驶并保持v_OUT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。

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。

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.

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’s过错pin 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_OUT到V._STL.。
3. V._OUTremains at V_STL.until the过错PIN被释放。
4. V._OUTis driven to V_stfor the duration of Self-Test Fault Request Time, ST_FR_TIME.
5. The device enters Self-Test Fault Request mode and V_OUTis driven to V_{坐了（h）}for ST_FPW_TIME and the过错pin is asserted.
6. V._OUTis driven to QVO for ST_FPW_TIME (10 ms) and the过错pin resets.
7. V._OUTis driven to V_坐（l）for ST_FPW_TIME (10 ms) and the过错pin 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.

图8中的应用示意图示出了这样的系统。A1365安装在层叠芯的间隙中，并用于感测由导体中的电流流产生的磁场。模拟输出，VOUT连接到ADC过错引脚连接到微控制器上的通用I / O引脚。假设I / O连接过错引脚在发生过电流的情况下发出系统中断。该中断提示微控制器通过断开导体中的电流与电流的连接来将系统放置在安全状态。

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The information contained in this document does not 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.