Advanced Power Management Using the ALS31300 and ALS31313 3D Hall-Effect Sensor ICs with I2C Output
Advanced Power Management Using the ALS31300 and ALS31313 3D Hall-Effect Sensor ICs with I2C Output
By Wade Bussing,
Allegro MicroSystems, LLC
Abstract
随着人机界面设备的扩散，对具有低成本，低功率和低形式因子的强大，非接触式传感解决方案的需求越来越大。Allegro Als31300和ALS31313 3D Hall效应传感器IC在SmallDDFN10封装中非常适合触发，按钮，旋转，操纵杆和2D滑块操纵杆应用。雷竞技最新网址高度可配置的电源管理选项，包括低功耗循环模式，睡眠模式和运动唤醒，使这些设备适用于电池供电的应用，如无用者，相机万向节以及控制台和移动游戏控制器。雷竞技最新网址本应用笔记讨论了可用的独特和高级的低功耗模式ALS31300andALS313133D线性霍尔效应传感器IC与i2C Allegro Microsystems提供雷竞技竞猜下载的C输出。
在本申请中的参考文献给ALS31300也适用于ALS31313，不同之处在于ALS31300在10触点DFN封装中提供，并且ALS31313设置在TSSOP-8封装中。
一世ntroduction
该ALS31300is a 3D linear Hall-effect sensor IC from Allegro MicroSystems. The ability to sense magnetic fields in three different axes allows the ALS31300 to be extremely versatile to sense linear motion on any axis or rotational motion using magnetic data from two axes. This application note will walk the user through application examples and device configuration tailored for specific application needs.
该ALS31300sensor may operate on supply voltages from 2.65 to 3.5 V and features highly configurable power management to maximize efficiency. The available power modes and typical supply currents for the ALS31300 are listed in Table 1.
Table 1: ALS31300 Power Modes
| Operating Mode | Mode Description | Suppy Current (Typical) |
| Active Mode | 该设备连续 updates magnetic and 温度数据。供应 current is constant. |
一世CC（活跃）≈3.4ma |
| Sleep Mode | 该device is in a near powered-off state. No magnetic or temperature data updates. Supply current is constant. |
一世CC.(SLEEP)≈ 14 nA |
| Low Power Duty Cycle Mode (LPDCM) |
该device toggles between fully active and inactive state. The device periodically wakes up to refresh magnetic 和温度数据。 |
一世CC(主动)≈ 3.4 mA 一世CC（非活动）≈12μA. |
该operating mode of the ALS31300 is determined by the value in the Sleep field: address 0x27, bits 1:0. These bits may be accessed at any time and are described in Table 2.
表2：睡眠寄存器
| Address | Bits | Value | Operating Mode |
| 0x27 | 1:0 | 0. | Active Mode |
| 1 | Sleep Mode | ||
| 2 | Low-Power Duty Cycle Mode (LPDCM) |
Sleep Mode
一世n sleep mode, the ALS31300 is in a near powered-off state where it consumes the minimum amount of current (14 nA, typical). In this mode, the device will still respond to I2C commands, but will not update magnetic or temperature data. Sleep mode is valuable in applications where the supply voltage cannot be disabled but minimal power consumption is required. The time it takes to exit sleep mode is equivalent to Power-On Delay time (t荚）。
低功耗循环模式（LPDCM）
一世n Low Power Duty Cycle Mode (LPDCM), the ALS31300 toggles between active and inactive states, reducing overall current consumption. The average ICC.for the ALS31300 during low power duty cycle mode varies based on the settings used, and may range between 12 μA to 2 mA (typical).
该diagram in Figure 1 shows the profile of ICC.as the ALS31300 toggles between active and inactive states during Low Power Duty Cycle Mode.
该duration t不活跃由场上决定Low Power Mode Count Max: address 0x27, bits 6:4. The ALS31300 offers eight discrete time frames for t不活跃。该T.ypical values for t不活跃列于表3中。典型的iCC.during t不活跃≈12μA.。
表3：LPDCM非活动时间（T一世NACTVE）
| Address | Bits | Value | T.不活跃（典型值）（ms） |
| 0x27 | 6.:4 | 0. | 0.。5. |
| 1 | 1 | ||
| 2 | 5. | ||
| 3. | 10. | ||
| 4. | 50. | ||
| 5. | 10.0. | ||
| 6. | 50.0. | ||
| 7. | 1000 |
该duration of tACTIVE, shown in Figure 1, is dependent on two settings:BW.选择以及活动频道的数量。
Magnetic sensing channels on the ALS31300 are enabled independently by writing ‘1’ to the频道x en，channel y en，and频道Z ZH.bits, listed in Table 4.
Table 4: Channel Enable Control
| Address | Bits | Value | Description |
| 0x02 | 8. | 1 | Enables Z Sensing Channel |
| 7. | 1 | Enables Y Sensing Channel | |
| 6. | 1 | 启用X感测通道 |
BW选择控制应用于采样磁数据的滤波量。表5中列出了BW选择和相应的更新速率（典型）的值。
Table 5: BW Select and Update Rate
| BW. 选择 Value |
1Channel 更新率 |
2通道 更新率 |
3.Channel 更新率 |
-3.dB Bandwidth |
|||
| μs. |
kHz | μs. | kHz | μs. | kHz | kHz | |
| 0. | 160. | 6. | 3.3.0. | 3. | 495. | 2 | 3.。5. |
| 1 | 8.0. | 13. | 17.0. | 6. | 255. | 4. | 7. |
| 2 | 40 | 25. | 9.0. | 11. | 135. | 7. | 14. |
| 3. | - | - | - | - | - | - | - |
| 4. | 64. | 16. | 138. | 7. | 20.7. | 5. | 10. |
| 5. | 32. | 31. | 7.4. | 14. | 111. | 9. | 20. |
| 6. | 16. | 63. | 42. | 24. | 63. | 16. | 40 |
| 7. | - | - | - | - | - | - | - |
为每个BW选择val产生的噪声性能ue is listed in Table 6.
Table 6: BW Select, Filtering Modes and Resulting Noise Performance (Input Referred)
| BW选择 Value |
FIR Enabled | Z通道 Noise (G) |
X / Y频道 Noise (G) |
| 0. | 1 | 1。5. | 4. |
| 1 | 1 | 2 | 5. |
| 2 | 1 | 2。2 | 7. |
| 3. | - | - | - |
| 4. | 0. | 2 | 6. |
| 5. | 0. | 2。5. | 8. |
| 6. | 0. | 3.。5. | 10. |
| 7. | - | - | - |
Configuring Low Power Duty Cycle Mode
This section will serve as a guide for configuring Low Power Duty Cycle Mode (LPDCM) based on a few top-level system requirements. Users should consider the goals of the specific application while configuring low power operation for the ALS31300. Screenshots in this section are taken from the ALS31300 Demonstration software available onAllegro’s Software Portal.
LPDCM Example
Assume the ALS31300 is used in a system that requires new magnetic data from two channels, X and Y, approximately every 500 μs with full resolution.
首先，启用x和y磁信道，在EEPROM选项卡下禁用Z通道。带宽选择值设置为代码为“0”以进行完整的测量分辨率。请参阅图2中的屏幕截图2.注意：所有通道都能启用Allegro Factory。
Next, set the value forLPM Count Max., which controls the duration of t不活跃。Referring back to Table 3, the appropriate code for t不活跃≈55μs是代码'0'。使用LPM Count Max Set，然后可以通过将睡眠字段设置为“2”的值来将设备放入LPDCM中。这些易失性设置显示在图3中的屏幕截图中。
由此产生的I.CC.配置文件显示在图4中的范围图中。包括非活动时间的关键参数（t不活跃）, active time (tACTIVE）， 一世CC(主动), and ICC（非活动）are highlighted.
注意我2即使ALS31300返回非活动状态，仍会处理C命令。这是可能的，因为我2C clock (SCLK) is processed in a separate domain from the
主系统时钟。
在图4中，通过使用具有差分探针的示波器在VCC上测量串联电阻上的电压来观察ICC（图5）。
Estimating ICC.Consumption
该average current consumption can be estimated based on the scope plot in Figure 4 and the typical values for tACTIVE, t不活跃, ICC(主动), and ICC（非活动）。Recall that the duration tACTIVE
是BW选择的设置和活动通道数的组合。
该T.ypical values for each of the parameters used in this example are summarized in Table 7.
表7：密钥LPDCM参数的典型值
| 参数名称 | Typical Value | Units |
| T.不活跃 | 50.0. | μs. |
| T.ACTIVE | 390. | μs. |
| 一世CC(主动) | 3.。4. | mA |
| 一世CC（非活动） | 12. | μA. |
For a complete table on timing versus BW Select and number of active channels, refer to Table 8 in Appendix A.
可以通过以下等式估计电流消耗，平均估计CC.in LPDCM:
Advanced Low Power Management Using the Interrupt Feature on ALS31300
该interrupt feature on the ALS31300 enables further system level power savings for applications requiring long battery life. This technique allows a system’s microcontroller to enter a low power state and wait for an interrupt from the ALS31300.
Assume that a system is monitoring for the presence of an applied magnetic field. For example, an electricity power meter may become inaccurate in the presence of large external magnetic fields. Assume this meter is sensitive to magnetic fields greater than 300 gauss (30 mT). Finally, assume there is a need for maximum current reduction in the system while on battery power due to a power blackout. A simplified block diagram is outlined in Figure 6.
一世nitialize Interrupt Conditions and ConfigureDevice for LPDCM
该ALS31300interrupt thresholds may be configured independently for all three axes (X, Y, and Z). For this example, each axes threshold will be set to a value equivalent to 300 gauss.
在仪表的正常操作期间，ALS31300将以其全部有源模式使用，睡眠= 0，因为功耗不如关注。在此模式下，设备正在消耗其典型的iCC(主动)at all times and continuously updating magnetic and temperature data.
假设电表检测来自电网的电源丢失并恢复为电池备份，但仍然需要监视篡改事件或大型外部字段。由于这些事件很有趣但不危险，我们可以选择将ALS31300放在最高效的LPDCM中。
First, set BW Select to the fastest state, code 7.
Next, configure the ALS31300 for one of its longest t不活跃通过将LPM计数Max设置为代码6.参考表3，我们可以看到代码6对应于A T不活跃T.ime of 500 ms.
Average ICC.使用等式1再次在此模式下估计消耗并用典型值代替符号。t的典型值不活跃with 3 channels enabled and BW Select = 7 can be found in Table 8 in Appendix A.
。
该system’s microcontroller may now be put into a deeper sleep state where it will be woken up by an active low by an active low Interrupt signal from the ALS31300 in the presence of field > 300 gauss.
由此产生的I.CC.profile is shown in the scope plot in Figure 8. The duration of tACTIVE与t相比很小不活跃它看起来像示波器上的两个小狭缝。一世2C transactions
still occur during LPDCM.
该scope plot in Figure 9 shows the Interrupt pin of the ALS3100 responding to an applied magnetic field > 300 gauss. The INT signal may be used as a wake up event for the meter’s micro, alerting the system to handle the tampering event.
附录A.
该full table of typical values for active time (tACTIVE) based on BW SELECT settings and the number of active channels are shown in Table 8.
Table 8: Typical Active Times (tACTIVE) vs. Number of Active Channels and BW Select Values
| BW选择 | Active Channels | 活跃时间（tACTIVE）（μs） |
| 0. | 3. | 592 |
| 2 | 390. | |
| 1 | 218. | |
| 1 | 3. | 31.3. |
| 2 | 224. | |
| 1 | 135. | |
| 2 | 3. | 18.8. |
| 2 | 141. | |
| 1 | 114. | |
| 3. | - | - |
| - | - | |
| - | - | |
| 4. | 3. | 263. |
| 2 | 19.1 | |
| 1 | 119. | |
| 5. | 3. | 164. |
| 2 | 125. | |
| 1 | 8.4. | |
| 6. | 3. | 114. |
| 2 | 9.1 | |
| 1 | 69. | |
| 7. | - | - |
| - | - | |
| - | - |
该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.