使用I2C输出的ALS31300和ALS31313 3D Hall效应传感器IC的先进电源管理
使用I2C输出的ALS31300和ALS31313 3D Hall效应传感器IC的先进电源管理
By Wade Bussing,
Allegro MicroSystems, LLC
Abstract
With the proliferation of human interface devices, there is a growing need for robust, non-contact sensing solutions that are low cost, low power, and low form factor. The Allegro ALS31300 and ALS31313 3D Hall-Effect Sensor ICs in small DFN10 package are ideally suited for trigger, push button, rotation, joystick, and 2D slider joystick applications. The highly configurable power management options, including low power duty cycle mode, sleep mode and wake on motion, make these devices well-suited in battery-powered applications such as drones, camera gimbals, as well as console and mobile gaming controllers. This application note discusses the unique and advanced low power modes available on theALS31300和ALS31313三维线性采用霍尔传感器ICs和我2C output available from Allegro MicroSystems.
References throughout this application note to the ALS31300 also apply for the ALS31313, except that the ALS31300 is provided in a 10-contact DFN package, and the ALS31313 is provided in a TSSOP-8 package.
介绍
TheALS31300is 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.
ALS31300传感器可以在电源电压下操作2.65至3.5 V，并具有高度可配置的电源管理，以最大限度地提高效率。ALS31300的可用电源模式和典型的电源电流列于表1中。
表1：ALS31300电源模式
| Operating Mode | Mode Description | Suppy Current (Typical) |
| Active Mode | The device continuously 更新磁性和 temperature data. Supply 电流是恒定的。 |
ICC(ACTIVE) ≈ 3.4 mA |
| 睡眠模式 | 该设备位于近 powered-off state. No magnetic or temperature 数据更新。供应 电流是恒定的。 |
ICC（睡眠）≈ 14 nA |
| 低功耗 循环模式 （LPDCM） |
设备之间切换 fully active and inactive state. The device periodically 醒来刷新磁性 和temperature data. |
ICC(ACTIVE)≈ 3.4 mA ICC(INACTIVE)≈ 12 μA |
The 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.
Table 2: Sleep Register
| Address | Bits | 价值 | Operating Mode |
| 0x27 | 1:0 | 0 | Active Mode |
| 1 | 睡眠模式 | ||
| 2 | 低功耗占空比模式 （LPDCM） |
睡眠模式
In 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命令，但不会更新磁性或温度数据。睡眠模式在电源电压不能禁用的应用中是有价值的，但需要亚博尊贵会员最小的功耗。退出睡眠模式所需的时间相当于上电延迟时间（tPOD).
低功耗循环模式（LPDCM）
In Low Power Duty Cycle Mode (LPDCM), the ALS31300 toggles between active and inactive states, reducing overall current consumption. The average ICCfor the ALS31300 during low power duty cycle mode varies based on the settings used, and may range between 12 μA to 2 mA (typical).
图1中的图表显示了I的配置文件CC由于ALS31300在低功耗循环模式期间在主动和非活动状态之间切换。
持续时间tINACTIVEis determined by the fieldLow Power Mode Count Max: address 0x27, bits 6:4. The ALS31300 offers eight discrete time frames for tINACTIVE. The typical values for tINACTIVEare listed in Table 3. Typical ICC在t.INACTIVE≈12μA。
Table 3: LPDCM Inactive Time (tINACTVE)
| Address | Bits | 价值 | tINACTIVE(typ) (ms) |
| 0x27 | 6：4 | 0 | 0.5 |
| 1 | 1 | ||
| 2 | 5 | ||
| 3 | 10 | ||
| 4 | 50 | ||
| 5 | 100. | ||
| 6 | 500 | ||
| 7 | 100.0 |
持续时间of t积极的, shown in Figure 1, is dependent on two settings:BWSelect和the number of active channels.
ALS31300上的磁感测通道通过写入“1”来独立启用channel x en, channel y en,和channel z en位，表4中列出。
Table 4: Channel Enable Control
| Address | Bits | 价值 | Description |
| 0x02 | 8 | 1 | Enables Z Sensing Channel |
| 7 | 1 | 启用y感测通道 | |
| 6 | 1 | Enables X Sensing Channel |
BW Select controls the amount of filtering applied to the sampled magnetic data. Values for BW Select and corresponding update rates (typical) are listed in Table 5.
表5：BW选择和更新率
| BW Select 价值 |
1通道 Update Rate |
2 Channel Update Rate |
3 Channel Update Rate |
-3 dB. 带宽 |
|||
| μs |
kHz | μs | kHz | μs | kHz | kHz | |
| 0 | 160 | 6 | 330. | 3 | 495 | 2 | 3.5 |
| 1 | 80 | 13 | 170 | 6 | 255 | 4 | 7 |
| 2 | 40 | 25 | 90 | 11 | 135 | 7 | 14 |
| 3 | – | – | – | – | – | – | – |
| 4 | 64 | 16 | 138 | 7 | 207. | 5 | 10 |
| 5 | 32 | 31 | 74 | 14 | 111 | 9 | 20 |
| 6 | 16 | 63 | 42 | 24 | 63 | 16 | 40 |
| 7 | – | – | – | – | – | – | – |
Resulting noise performance for each BW Select value is listed in Table 6.
Table 6: BW Select, Filtering Modes and Resulting Noise Performance (Input Referred)
| BW Select 价值 |
FIR Enabled | Z Channel Noise (G) |
X/Y Channel 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 | – | – | – |
配置低功耗循环模式
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 on快板的软件门户。
LPDCM示例
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.
First the X and Y magnetic channels are enabled and the Z channel is disabled under the EEPROM tab. The Bandwidth Select value is set to code ‘0’ for full measurement resolution. Refer to the screenshot in Figure 2. Note: All channels come enabled from the Allegro factory.
Next, set the value forLPM Count Max, which controls the duration of tINACTIVE. Referring back to Table 3, the appropriate code for tINACTIVE≈ 500 μs is code ‘0’. With LPM Count Max set, the device may then be put into LPDCM by setting the Sleep field to a value of ‘2’. These volatile settings are shown in the screenshot in Figure 3.
The resulting ICCprofile is shown in the scope plot in Figure 4. Key parameters including inactive time (tINACTIVE), active time (t积极的), ICC(ACTIVE), and ICC(INACTIVE)突出显示。
Note that the I2C commands are still processed even while the ALS31300 returns to the inactive state. This is possible because the I2C时钟（SCLK）在单独的域中处理
main system clock.
In Figure 4, ICC was observed by measuring a voltage across a series resistor on VCC using an oscilloscope with a differential probe (Figure 5).
估计I.CC消费
可以基于图4中的范围绘图和T的典型值来估计平均电流消耗积极的，T.INACTIVE, ICC(ACTIVE), and ICC(INACTIVE). Recall that the duration t积极的
is the combination of settings for BW Select and the number of active channels.
The typical values for each of the parameters used in this example are summarized in Table 7.
Table 7: Typical Values for Key LPDCM Parameters
| Parameter Name | 典型价值 | 单位 |
| tINACTIVE | 500 | μs |
| t积极的 | 390 | μs |
| ICC(ACTIVE) | 3.4 | 嘛 |
| ICC(INACTIVE) | 12 | μ一 |
For a complete table on timing versus BW Select and number of active channels, refer to Table 8 in Appendix A.
Current consumption may be estimated by the following equation, Average ICCin LPDCM:
Advanced Low Power Management Using the Interrupt Feature on ALS31300
ALS31300上的中断功能可以为需要长电池寿命的应用程序提供进一步的系统级功率节省。亚博尊贵会员该技术允许系统的微控制器进入低功率状态并等待来自ALS31300的中断。
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.
为LPDCM初始化中断条件和CoverseDevice
可以针对所有三个轴（x，y和z）独立配置ALS31300中断阈值。对于该示例，每个轴阈值将被设置为相当于300高斯的值。
During normal operation of the meter, the ALS31300 will be used in its full active mode, Sleep = 0, since power consumption is not as much of a concern. In this mode, the device is consuming its typical ICC(ACTIVE)at all times and continuously updating magnetic and temperature data.
Assume that the electricity meter detects a loss of power from the grid and reverts to battery backup, but it is still necessary to monitor for tampering events or large external fields. Since these events are interesting but not dangerous, we may choose to put the ALS31300 in its most efficient LPDCM.
首先，将BW SELECT设置为最快状态，代码7。
Next, configure the ALS31300 for one of its longest tINACTIVEtimes by setting LPM Count Max to code 6. Referring back to Table 3, we can see code 6 corresponds to a tINACTIVE时间为500毫秒。
Average ICCconsumption is again estimated in this mode using Equation 1 and substituting the symbols with typical values. Typical value for tINACTIVE使用3个通道，BW Select = 7可以在附录A中找到。
.
现在，系统的微控制器现在可以进入更深的睡眠状态，在那里它将通过来自ALS31300的有效低中中断信号在存在的现场> 300高斯的存在下唤醒。
The resulting ICCprofile is shown in the scope plot in Figure 8. The duration of t积极的is so small in comparison to tINACTIVEthat it appears as two small slits on the oscilloscope. I2C Transaction.
在LPDCM期间仍然发生。
图9中的范围图显示了响应于应用磁场> 300高斯的ALS3100的中断引脚。int信号可以用作仪表微的唤醒事件，警告系统处理篡改事件。
APPENDIX A
基于BW选择设置和活动通道数的活动时间（Tactive）的典型值的完整表如表8所示。
Table 8: Typical Active Times (tACTIVE) vs. Number of Active Channels and BW Select Values
| BW SELECT | Active Channels | Active Time (t积极的) (μs) |
| 0 | 3 | 592 |
| 2 | 390 | |
| 1 | 218. | |
| 1 | 3 | 313. |
| 2 | 224. | |
| 1 | 135 | |
| 2 | 3 | 188 |
| 2 | 141 | |
| 1 | 114 | |
| 3 | – | – |
| – | – | |
| – | – | |
| 4 | 3 | 263 |
| 2 | 191 | |
| 1 | 119 | |
| 5 | 3 | 164 |
| 2 | 125 | |
| 1 | 84 | |
| 6 | 3 | 114 |
| 2 | 91 | |
| 1 | 69 | |
| 7 | – | – |
| – | – | |
| – | – |
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.