使用A1337角度传感器IC（AN296116）的低功耗和转弯感应
使用A1337角度传感器IC（AN296116）的低功耗和转弯感应
通过Alihusain Sirohiwala，Al雷竞技竞猜下载legro Microsystems
Introduction
从工业自动化和机器雷竞技最新网址人到电子动力转向（EPS）和电机位置感测的许多应用需要监视旋转目标的角度。任何成功的角度测量系统的设计都需要基于用户的要求。雷竞技最新网址申请笔记AN269115andAN269121cover the use of Allegro angle sensor ICs in on-axis and off-axis magnet configurations. This application note covers the use of theAllegro A1337 angle sensor ICfor batterypowered applications (automotive or non-automotive) that require the sensor to operate in multiple mission modes.
即使在关键条件下，也需要传感器操作的汽车系统
Certain automotive angle sensing applications require the ability to track angular position even in key-off conditions. In the key-off state, most voltage regulators in the vehicle are not operational. Therefore, sensors that must operate in the key-off state are often powered directly from the car battery (12 V). Examples of such applications include:
- Seat-belt passive safety systems
- EPS motor position
通常，这些电动机和座椅带系统换档，以便通过角度传感器IC计算多个角度传感器旋转。因此，A1337包括计数磁体的旋转匝的电路。当传感器IC连接到汽车电池时，它们还必须具有低功耗模式，可实现有效的电池使用。通常，即使当车辆处于键关闭状态时，传感器IC也必须跟踪磁铁的匝数（TCS）。A1337监视并跟踪TCS，即使设置为低功耗模式也是如此。当在键盘或键盘模式下使用A1337时，这将确保系统可以准确且始终一致地跟踪方向盘位置或座椅带扩展。传统上，通过相对复杂的机械和电子元件的组合来实现这种关键要求。A1337可以通过执行绝对角度测量和TCS的跟踪来降低系统级复杂性并消除许多系统组件，同时在车辆键关闭时保持低电池功耗（85μA）。
A1337概述
The A1337 is a 360° angle sensor IC that provides contactless high-resolution angular position information based on magnetic Circular Vertical Hall (CVH) technology. It has a system-on-chip (SoC) architecture that includes a CVH front-end, digital signal processing, and SPI, SENT, and PWM outputs. It also includes on-chip EEPROM technology for flexible end-of-line programming of calibration parameters. The A1337 is ideal for automotive applications requiring 0° to 360° angle measurements, such as electronic power steering (EPS), rotary shifters (PRNDLs), seat-belt tensioners, and throttle systems. The A1337 angle sensor device is designed to support a wide variety of applications and has multiple operating modes, organized by output format or by power consumption. By output format, the A1337 supports SPI, SENT, PWM, and Manchester interfaces. For each of these interfaces, the A1337 has the ability to report either the direct angle output (12-bit digital angle output reported over the selected output interface) or a Turns Count (TC) output, which is a quantized tracking count of the number of turns made by the magnetic target in either the clockwise or counter-clockwise direction. By power consumption, the A1337 features a Normal Power Mode, a Low Power Mode, and an ultra-low power Transport Mode.
正常电源模式
In Normal Power Mode, the IC draws maximum current (nominally 8.25 mA—see Normal Mode Supply Current specification in the A1337 datasheet for more details) to operate its full feature set, and updates the angle output register at the fastest rate as selected by RPM mode and AVG settings (see the A1337 programming
参考更多详情）。
Low Power Mode
低功耗模式对于电池的应用非常有用cations where the task of tracking the target’s rotation can be delineated into one of two mission modes. The first mission mode would be similar to an angle tracking mode, where the sensor tracks the output at full bandwidth and provides its measure of the angular output at full resolution. The second mission mode can be considered as a turns-tracking mode. In this mode, the sensor does not need to track the angle at full resolution—it is sufficient to track the Turns Count value of the target. The size of one turnscount unit can be preselected via EEPROM setting in the A1337 to be either 180 or 45 degrees. The A1337 tracks ±1280 turns in both directions. In Low Power Mode, the A1337 is mostly held in a lower quiescent current consumption state. The IC does not provide normal angle readings over the SPI, SENT, or PWM interfaces, but wakes up periodically to check for the occurrence of Turns Counts. The off-time of the Low Power Mode operation can be adjusted by the user based on the application, by programming on-chip EEPROM memory. Figure 2 shows Average ICCin μA versus the programmable off-time tOFF。
Transport Mode
在长期存储和/或运输期间，某些电池供电的应用需要雷竞技最新网址从IC的IC尤其低功耗（例如，当新车从装配线运输到经销商时）。为了满足这种需求，A1337采用超低功耗模式，称为传输模式。传输模式用于将A1337放入深度睡眠状态以进行超低功耗。在此模式下，传感器IC不跟踪角度或转弯计数。通常，IC在运输模式下消耗每芯的30μA电流。
唤醒别针
A1337还提供尾部输入引脚。该引脚旨在从低功耗模式唤醒设备，在电机加速度过高的特殊情况下，该系统不能在下一个定期唤醒之前等待整个低功率睡眠时间来过期。当唤醒引脚上的电压阈值超过V时WAKE(HITH)，IC将从低功耗模式唤醒，然后开始追踪正常电源模式的转弯。该引脚通常连接到来自所使用的电动机的电动机电压信号的滤波版本。这允许在高加速度事件的情况下，从电动机到匝数计数电路的快速反馈。下面示出了星形3相电动机的后部EMF的符号波形表示，以及样品滤波电路。
Transitioning Between Modes
The A1337 is designed so that it can transition between Normal Power Mode (NPM), Low Power Mode (LPM), and Transport Mode (TPM) based on either a command from the system microcontroller, by magnetic target rotation, or by exceeding the WAKE pin threshold, VWAKE(HITH)。这种双重方案确保了由于在传感器处于低功率模式下，由于目标旋转太快，因此有价值的TC信息不会丢失。为了更好地理解这一点，考虑一些基于的情景
the state diagram shown in Figure 3, as well as the information shown in Table 1. Assume that the sensor is powered up and in NPM. It would therefore be able to provide all the functionality as described under NPM in Table 1. Now, if the controller decided that to save power it should enter LPM, then it would have to satisfy all the conditions outlined in branch A of Figure 3 in order to enter LPM. In other words, the A1337 SPI lines would have to be held low for >50 μs, the WAKE pin voltage
在A1337 IC上必须低于阈值VWAKE(LOTH)，并且磁铁的目标RPM将小于平均速度AWAKE(TH)。If all these conditions were met, then the IC would transition into LPM. While in LPM, the IC would be able to support the TC tracking functionality
as described in Table 1. If the system now needed to wake up from LPM and re-enter NPM, it would need to then satisfy any one of the conditions outlined in branch B of Figure 3—in other words, initiating activity on SPI pins, or rotating the target faster than SAWAKE(TH)，或施加高于V的电压WAKE(LOTH)on the WAKE pin. In a similar manner, the system can navigate between NPM, LPM, and TM, by meeting the appropriate conditions as specified by branches A, B, C or D of the state diagram.
