电流传感器常见问题

霍尔效应的存在是一个电压时an external, perpendicular magnetic field is applied to a current carrying conductor. The conductor, or the Hall Element, is biased with a constant current. As magnetic field changes, a change in voltage across the hall element occurs. This voltage can then be amplified and conditioned to provide an output that is related to the magnetic field. Using this principle, magnetic field can be concentrated perpendicular to the hall element using integrated packaging, ferromagnetic cores, or coreless busbars. Hall effect current sensors have the advantage of inherent isolation, low power loss, and stability across temperature while providing an analog output voltage that can be monitored by a microcontroller.

Parts can be ratiometric or non-ratiometric. Ratiometric indicates that the device sensitivity is proportional to the device supply voltage, VCC. In addition, the device output at 0 A, also called V_iout（q）, is nominally equal tovcc / 2。Non-ratiometric devices will have VIOUT(Q) and sensitivity values stable over V_CCvariations within the specified input voltage range. Ratiometry can be useful when the input voltage of the sensor is on the same line as the ADC reference voltage. Non-ratiometric parts are useful in applications where the sensor input voltage is noisy or unstable. Unstable V_CC如果该部件比率，将产生嘈杂的输出。

The three main types of error in current sensors are defined as:

Sensitivity Error:E_sens=（（（测量灵敏度）/ sen）-1）×100（％）

Offset Error:V_OE= Measured QVO – QVO

Total Output Error:E_tot=（（v_出去–V_出去IDEAL）/（SENS_理想的×I._P))× 100(%)

Thisapplication notegoes more in depth on sources and definitions of error.

On the Allegro Current Sensor device homepage, navigate to the “Part Number Specifications and Availability”. Select “View Data” on the desired gain option. The MSL rating is included in the “Materials Declaration Report”.

While MSL rating are specifically for surface mount parts, Allegro does qualify and provide a through hole equivalent (THD) for non-surface mount parts that directly correlates to the standard MSL ratings.

One of the key benefits of Hall Effect current sensors is their inherent galvanic isolation. Because there is no electrical connection between the primary current path and the signal circuitry, much higher working voltages are available. There are several isolation parameters or tests included in the current sensor device datasheets such as:

Dielectric Surge Strength- 可以处理已知上升时间，宽度和幅度的脉冲的电压量。

Dielectric Strength- The amount of voltage and time that can be withstood before electrical breakdown occurs. This is tested for a set amount of time (usually 60 seconds) while measuring leakage current to ensure breakdown has not occurred.

工作电压- 可以连续应用于设备的最大电压。它通常具有DC，峰值与峰值和RMS电压的指定值。

Isolation characteristics are specific to the package of the device. Below is a table summarizing the various packaging types offered by Allegro and their isolation characteristics as well as other important package information.

Package Descriptor	SOICW-16. LA.	SOICW-16. 嘛	SOICW-16. 马克	SOIC-8 LC1.	SOIC-8 LC2.	QFN-12. EXB	7-pin PSOF LR.	5-pin CB
Picture
尺寸	10.3x10.3mm.	10.3x10.3mm.	11.3x13mm	4.9x6mm	4.9x6mm	3x3mm.	6.4x6.4mm	14x22mm.
导体抵抗	0.85mΩ.	0.85mΩ.	0.27 mΩ	1.2 mΩ	0.65 mΩ	0.6mΩ.	0.2 mΩ	0.1mΩ.
Dielectric Strength	rms.3600 V.	rms.5000 V	rms.5000 V	rms.2400 V.	rms.2400 V.	NA	NA	rms.4800 V.
工作电压	DC870 V rms.616 V.	DC1550V rms.1097 V	DC1618 V. rms.1144 V	DC420 V. rms.297 V	DC420 V. rms.297 V	DC100 V. rms.70 V	DC100 V. rms.70 V	DC1358 V rms.700 V

Allegro也提供核心和无芯场传感器。These devices can sense currents >1000A and achieve >5000VRMS of dielectric strength isolation.

The part output will continue to increase or decrease until it reaches a high (current > IPR) or low (current < I_PR）饱和点，在哪里_PR是该部件的电流传感范围。电压输出高/低（v_OH/V_OL），有时被称为输出饱和电压（V._SAT(H/L)), is defined as the voltage that sensor output, V_IOUT，不会导致结果增加/降低电流。这可以在下图中看到。请注意，更改灵敏度不会改变饱和电压。

v的线性性能的功能范围_IOUT及其相关的数据表参数，来自-i有效_PR到+ I._PR。It is possible for the output to report voltages beyond the full-scale measurement until the saturation point, but parameters are not guaranteed beyond the full scale measurement.

Every Allegro current sensor will have a power on time specified in the datasheet such as the example below:

Power-On Time, t_PO, is defined as the time interval between a) the power supply has reached its minimum specified operating voltage (V_cc（min）), and b) when the sensor output has settled within ±10% of its steady-state value under an applied magnetic field. An example of the output and supply voltage can be seen in the scope capture below:

TheMagnet, Concentrator and Magnetic Shield SuppliersAllegro网站上的页面提供了供应商列表和推荐磁铁的概述。此列表包括有关核心/集中器和屏蔽供应商的信息。

Allegro电流传感器分别有两个范围变体，双向和单向，分别用零件后缀B和U识别。双向部件可以感测积极和负电流，而单向部件只在一个方向上感知。当电流在负方向上并且最大时，双向部件的输出将最小，当电流在正方向上满量程时。单向部件的输出将在最小的情况下，如果电流小于或等于零，当电流在正方向上满量程时最大值。双向部件可用于检测负下冲或有益于电流在两个方向流动的系统。当不需要在负方向上感测电流时，单向设备可用于提高灵敏度。

Every Allegro current sensor includes pins for V_CC，地面（GND），V_出去,和被感测到初级电流的路径，如果是集成传感器。有些部件包括额外的引脚，用于增强功能。这些引脚列表包括：

VREF/VZCR-提供零电流输出电压（V._iout（q）) to a reference pin. This allows for differential measurement and the user to know the zero-current voltage for the output channel V_IOUT。(ACS37002,ACS730)

FAULT /Over Current Fault (OCF)- open drain output that will pull low when a current threshold has been met. The fault output may be latched or unlatched in operation (ACS37002,ACS71240,ACS720,ACS732,ACS733,A1365)

V_OC- 某些部件可以使用外部电压选择过电流故障阈值。这是通过连接到V的电阻梯完成_CCpin. (ACS37002,ACS720,ACS732,ACS733)

Gain Select- Some parts can change the gain depending on the logic applied to the gain select pin which looks for a high or low input (ACS37002）。

FILTER- By attaching an external capacitor, the V_出去滤波器位置可以设置（ACS720,ACS724 / 5.)

Noise

噪音（输入参考[mA_rms.[MV_rms.]) is the root mean square value of the noise on the output evaluated at the specified bandwidth.

Noise Density

噪声密度（输入参考[（μA_rms.（√hz]或输出参考[（μV）_rms.）/√Hz]）是噪声作为频率的函数。大致从噪声密度转换为噪声，乘以噪声密度√（带宽*π/ 2）（请注意，在较低频率下，约<1kHz，闪烁噪声或1 / f噪声，起到一个因素，并将影响整体噪音performance, i.e. not all noise is removed with a DC input).

设备的分辨率相当于所提到的噪声输入[mA_rms.] at the desired bandwidth. If a device is specified with noise density, convert to noise by multiplying noise density by√(bandwidth*π/2)。如果设备被指定为引用的输出，则通过敏感性除以引用的输入。

计算分辨率时需要考虑的另一个因素是ADC的能力，其中电流传感器输出连接。AMPS中传感器输出的ADC分辨率等于：

（ADC范围[MV]）/（器件SECT [MV / A] * 2^{ADC ENOB [位] -1})

As an example, calculate the resolution of theACS732KLATR-20AB-Tat 1MHz bandwidth using a 5 V ADC with 11.5 effective number of bits. The ACS732 is specified with a noise density of 55 (µA_rms./√Hz。

Multiply this value by √(1MHz * π/2) to get a noise of 69 mA_rms., which gives the resolution of the sensor output.

接下来，计算分辨率=的ADC分辨率(5000 mV) / ((100 mV) / A * (2^11.5-1)）。

This results in an ADC resolution of 34.5 mA. When calculating the total resolution of the system, take the maximum of these two calculations, or in this case, 69 mA.

Low pass filtering of the Allegro current sensor output will decrease the noise but at the cost of device bandwidth. If a specific noise level or resolution is desired, solve for bandwidth (BW) in the following equation:desired noise = noise density * √(BW*π/2)。

Next, pick R and C values that generate the desired bandwidth. The bandwidth of an RC filter is equal to1 /（2 *π* r * c）。It is important to use an R value that is low enough to not affect the ADC reading. Because ADC’s generally have high input impedance, a value of around 1Kohm or less is typically acceptable.

• 验证数据表中的噪声如何。例如，噪声可能取决于V上的电容器_出去，如下面的规格。

• Increase the capacitance on V_出去。The datasheet will include a value for the maximum output capacitance that can be connected to V_出去，如下面的规格。

• If changing the capacitance does not fix the problem, layout should be examined. If the V_出去signal has a long trace to the ADC or measurement instrument, there may be other signals interacting with the output signal. Attach an oscilloscope as close as possible to the output of the current sensor and monitor the noise directly at the part output.
• 另一个潜在问题是传感器的不稳定输入电压。比率部件将对器件输出信号转移噪声输入电压。监控V._CC电流传感器的引脚检查输入不稳定输入。确保正在使用正确的旁路电容值，并尽可能地放置在PCB上的部分。
• 另一个噪音来源可能来自杂散磁场。参考Question 1 of the Design Support部分to learn about mitigating stray fields.

Listed in the datasheet for each device is a Selection Guide, typically located on page 2 or 3. While there is some variation from device to device in what is included in the device selection guide, some primary attributes of the selection guide are the part number, sensitivity (Sens), optimized current range (only applicable to integrated conductor sensors), operating temperature (T_A），包装类型和电源电压（如果设备有5 V和3.3 V变型）。This table can be used as a guide when selection the current sensor for an application.

例子：

基于核心（ACS70310.) Selection Guide from device datasheet:

有两种基本的快板电流传感器命名schemes, one for integrated (ACS71240, ACS724, ACS37002, etc.) and one for core-based sensors (ACS70310, A1365, etc).

常见的命名组件到基于核心和核心的传感器：Allegro当前传感器以ACS开头（传统A1363 / 5/6 / 7除外），其次是三到五位部分编号。零件号后跟一个字母以指示传感器的工作温度范围。温度范围指定之后是包装指示器，可以是两个/三位数字。在包装指定之后，集成传感器然后有两个字母指定可用于可用的包装/送货选项，基于核心的传感器将有一个有关领域选项的字母指定。接下来，集成传感器具有两个/三位数电流范围值，基于核心的传感器具有修剪的灵敏度值。然后是传感器的方向性，双向（B）或单向（U）。接下来是设备的标称电源电压电平。包含在零件名称的末尾是自定义功能（自定义故障级别，设置极性，客户可编程等）。有关设备零件编号的更多信息，请参阅设备特定数据表。请注意，像ACS722 / ACS723，ACS724 / ACS725和ACS732 / ACS733一样，遗留设备，不具有名称的双向或单向指定，也不具有标称电源电压的指定。 Different part numbers were made for 3.3 V and 5 V variants (i.e., the ACS724 is a 5 V device while the ACS725 is a 3.3 V device but these parts have identical functionality).

命名方案的示例：

Core Based (ACS70310.）：

Integrated (ACS71240）：

Legacy Integrated (ACS724vs.ACS725，请注意选择指南中没有电源电压指示）：

A min/max limit guarantees that no devices will be above or below the min/max value when leaving the Allegro factory. Typical values are mean ± 3 sigma. This means that 99.7% of devices will fall within the typical values and none will fall outside the min/max limits within the specified operating temperature range, input voltage, or any other test conditions.

It is also important to note that Sensitivity Error (ESENS) and Total Error (ETOT) are specified at a given current (typically the full-scale current, or half-scale current). Error results may vary with different applied currents. The main example of this is Total Output Error at lower currents. For example, if the full-scale range of a part is 20A and there is a 5% maximum Sensitivity Error and 1A maximum Offset Error, maximum Total Output Error = 20 A * (5% / 100) + 1 A = 2 A or 10% of the full-scale applied current of 20 A. At 5 A applied with the same sensitivity error and offset, Total Output Error = 5*(5% / 100) + 1 A = 1.25 A or 25% of the full-scale applied current.

以下 application note为Allegro电流传感器包提供表征数据。此应用笔记包括Allegro演示板上拍摄的数据。当定义适用于特定应用程序和当前要求的正确Allegro电流传感器包时，本文档很有用。

The absolute maximum amount of current that can flow through the package is different than the range of current a device can sense. The maximum allowable current is dependent on package and PCB layout and is a function of ambient temperature. Refer to常见问题解答热部分的问题1有关确定Allegro电流传感器最大允许电流的信息。当流过电流大于优化电流传感范围时，设备的输出将饱和。参考常见问题解答一般部分的问题7for a further explanation on output saturation.

A- allegro.
S- 传感器
E– Evaluation
K- 成套工具

导航到Allegro Microsystemshomepage。Allegro current sensor demo boards begin with the “ASEK” designation. For example, if a ASEK37800KMAC‐015B5‐SPI demo board is required to evaluate the ACS37800KMACTR-015B5-SPI, search ASEK37800 in “Check Stock” search bar on the top right corner of the Allegro homepage.

搜索“ASEK37800”将为所有可用的ASEK37800演示板提供结果。点击购物车图标被路由到Digikey网站以进行购买。

在“设备主页”上，单击“设计支持工具”的链接，如下图所示：yabo亚博网站

If the demo board has a user guide it will be available in the Design Support Tools with a downloadable link as shown below:

All components on the demo board will be rated at or above the max temperature rating of the current sensor under test. The current rating of the demo board will depend on the package of the current sensor and ambient temperature. The followingapplication noteprovides characterization data for current sensor packages on Allegro demo boards at various ambient temperatures.

在每个Allegro电流传感器的设备主页上是一个设计支持部分，位于网页底部附近。yabo亚博网站在这里，有一个包含设备的ASEK演示板的Gerber文件的ZIP文件。Gerber文件是包含PCB设计的每个板层的信息的文件。

解压缩Gerber文件文件夹后，将有一个Fab文件。该FAB文件包含有关演示板布局的信息以及关于铜厚度，PCB层计数的信息，包括演示板属性。

In each device datasheet, there is a PCB layout and thermal application section that is specific to that device and package.

Related Application Notes:

1. 使用ACS71X电流传感器IC时管理外部磁场干扰
2. 使用Allegro电流传感器IC时最小化共模场干扰的技术(ACS724 and ACS780)
3. 无核霍尔效应电流传感器IC中的共模场抑制

参考设计支持FAQ部分的问题1yabo亚博网站to learn about mitigating stray fields.

On the specific Allegro current sensor device homepage, navigate to the “Part Number Specifications and Availability”. Select “View Data” on the desired gain option. The package weight is included in the “Materials Declaration Report”.

On the device homepage of the desired Allegro current sensor, located near the bottom of the web page, is a Packaging section. In the Packaging section, there is typically an image of the package the device is housed in (more than one if the device is offered in multiple packages). Step files for the device package can be found here.

If the step file is not located on the device homepage, please refer to thevip亚博 在Allegro网站上。

Acquiring a UL certification indicates that Allegro current sensors have been tested to applicable standards; UL is globally recognized in their ability to provided accreditation to productions in the industry. Allegro current sensors housed in the MA, LC, MC, LA, and CB packages have been certified to related UL standards 60950-1, 2nd Edition and 62368-1, 1st Edition (MA only).

位于Allegro电流传感器的设备主页，位于MA，LC，MC，LA和CB封装中，是UL Compliance和UL CB测试证书的UL证书。

Certificates of Compliance verify that devices have been tested by UL in accordance with UL standard 60950-1 and UL standard 62368-1 (MA only). CB Test Certificates provide the UL certified working voltage for basic and reinforced insultation numbers as well as the maximum rated isolation voltage.

参考“Allegro产品的焊接方法”application note on the Allegro website anddownloaded here。

• LA.has the highest sensitivity with the Hall element closest to the conductor
  • Fill-chip locates top of die closest to the leadframe
• 嘛has high internal isolation
  • 2 layers of polyimide insulation and 3 layers of insulating adhesive
• 马克has the lowest internal conductor resistance
  • 更长的爬电以更好的工作电压

Also refer toQuestion 6 of the General Question section常见问题解答更多包裹信息。

有几种方法可以开始产品选择流程。第一个将基于所需的隔离或包装大小。下表提供了可用包（不包括字段传感器）的概述。

Package Descriptor	SOICW-16. LA.	SOICW-16. 嘛	SOICW-16. 马克	SOIC-8 LC1.	SOIC-8 LC2.	QFN-12. EXB	7-pin PSOF LR.	5-pin CB
Picture
尺寸	10.3x10.3mm.	10.3x10.3mm.	11.3x13mm	4.9x6mm	4.9x6mm	3x3mm.	6.4x6.4mm	14x22mm.
导体抵抗	0.85mΩ.	0.85mΩ.	0.27 mΩ	1.2 mΩ	0.65 mΩ	0.6mΩ.	0.2 mΩ	0.1mΩ.
Dielectric Strength	rms.3600 V.	rms.5000 V	rms.5000 V	rms.2400 V.	rms.2400 V.	NA	NA	rms.4800 V.
工作电压	DC870 V rms.616 V.	DC1550V rms.1097 V	DC1618 V. rms.1144 V	DC420 V. rms.297 V	DC420 V. rms.297 V	DC100 V. rms.70 V	DC100 V. rms.70 V	DC1358 V rms.700 V

其他产品选择流可以从所需的电流传感电平开始。Allegro为各种电流传感级别的登陆页，包括：

• 0-50A Sensors
• 0-400A电流传感器
• 0至> 1000A场传感器

The目前的传感器创新also highlights the benefits of the different product families.

调试杂散磁场时，检查传感器是否是单个或双霍尔技术，通过检查设备特定数据表的功能框图。

单堂和流浪领域：

因为Allegro电流传感器使用霍尔效应来测量电流，所以在测量的电流外部的霍尔元件上看到的任何附加磁场都会影响传感器的输出。这些附加磁场通常称为杂散或普通磁场。杂散磁场最常见的原因是在电流传感器附近存在高电流迹线或导线。为了近似由电流携带线引起的误差，将迹线的磁场模拟为无限线B = µ* (I / (2π×d))。

B是高斯（g）的磁场，µis the permeability of free space in G equal to4π* 0.001,I是安培的当前，还有吗？d从电线上的点到垂直于电线的霍尔元件的线路的距离。一旦磁场是已知的，乘以磁耦合因子[g / a]（在大多数数据表中提供），它将导致放大器中的绝对误差。一旦估计错误，可以通过去除杂散场产生电线或迹线并重新测试传感器输出来执行测试。如果不能移除迹线或电线，则另一个解决方案是将传感器从电路板上拉出并将部分从疑似电流携带线上脱离PCB。最后，可以通过将铁物质放置在传感器周围以阻挡杂散场来使用屏蔽。

Thisapplication notedescribes in more detail the effects of magnetic field interference and shielding.

Dual Hall and Stray Fields:

Allegro也提供sensors with dual hall elements to mitigate stray field error. Two Hall elements are used differentially and placed on opposite sides of the current loop. This allows the common magnetic field to be removed allowing output voltage to be significantly unaffected by the common field. Although dual hall elements minimize stray field error, they do not entirely eliminate the potential of error induced by stray field. The same testing/mitigation techniques in the previous paragraph can also be used when debugging dual hall sensors.

Thisapplication note更详细地解释了如何在使用双霍尔元素的传感器时估计和减轻公共磁场。

Allegro为大多数Allegro电流传感器提供LTSPICE模型。以下关联将下载一个zip文件夹，其中包含整个Spice模型库，用于Allegro当前传感器。阅读“zip文件夹中包含的”allegro_acs_lt_guide.pdf“，以便详细步行，以便在LTSPICE中获取开始以及如何使用Allegro零件。

This笔记gives an overview, guidelines, and simulation results for designing with a bus bar.

Allegro也提供an在线交互式建模l帮助设计无芯解决方案的母线。

This笔记提供用于设计核心/集中器的概述和指南，与Allegro现场传感器配对。

以下is a check list to follow to verify the proper output of an Allegro current sensor:

• Is the input voltage above the minimum and below the maximum specified in the datasheet? Adjust the input voltage to match the typical VCC value in the datasheet.
• 输入电流是否与数据表的典型值匹配？如果电流低于预期，则输入电源和传感器之间可能存在开路。如果电流高于预期，则输入下沉电流可能存在其他东西，并防止设备正确偏置。验证供应连接到零件。
• When the device is biased on correctly, but no current is applied, what is the output of the device? Ensure that when in this state, the device output matches the zero-current output voltage (V_iout（q）) that is specified in the datasheet. If this does not match, measure the resistance from the output to ground and make sure nothing is pulling the output low. Also try to resolder the sensor or replace with another part to see if the problem persists. This will verify if the issue is part or application related.
• If V_iout（q）是正常的，是数据表规范内设备的灵敏度吗？快速测试灵敏度，应用0 A和测量v_IOUT，然后应用已知的电流和remeasure v_IOUT。The slope of these two points is the sensitivity in mV/A. To troubleshoot issues with sensitivity, ensure that the resistance of the current path being sensed is as expected by measuring with an ohmmeter. Faulty soldering or a stray trace could lower the resistance through the conductor being measured and introduce error.

其他潜在问题包括噪音（refer to the Noise section of the FAQ）和杂散磁场（请参阅常见问题解答的设计支yabo亚博网站持部分）。

Essentially every shunt solution can be replaced with an integrated Hall Effect sensor simply by routing the current trace through the integrated current sensor instead of through an external shunt. The few shunt solutions that may not be practical for an integrated Hall Effect sensor include ultra-low current resolution (in the uA’s) or ultra-high speed (>1Mhz).

The key benefits of switching from a shunt solution to an integrated Hall Effect solution are increased isolation, decreased layout size, and decreased design complexity. Most shunt solutions cannot exceed more than 100 V common mode voltage without the use of an isolation amplifier that requires external isolation circuitry. Compare that to Hall Effect current sensors, which offer inherent isolation from the current path to the signal pins. Switching to a Hall Effect sensor also eliminates the need for an external shunt and input filtering. This lowers the layout space as well as the design complexity.

There are many ways to measure current in a system, but the following table highlights and compares the main current sensing solutions:

Located on theAllegro Customer Portalare programmer GUIs/DLLs for Allegro customer programmable sensors. In addition to programming software for customer programmable devices, the Allegro Customer Portal has helpful design tools including user guides and interactive design tools.

TheASEK20is a device used to program and evaluate customer programable Allegro current sensors (the ASEK20 can be used for angle position, linear position, and digital position sensors). The ASEK20 is used in combination with the device specific daughterboard (which are available separately from the ASEK20). The ASEK20 is a benchtop validation and programming tool useful in characterizing and understanding the performance of Allegro current sensors. The ASEK20 is also useful in calibrating Allegro current sensors in the field. Device specific software applications can be found onAllegro的软件门户。

客户可编程Allegro当前传感器，可与ASEK20一起使用：

1. ACS70310.
2. ACS70311.
3. ACS71020
4. ACS37800.
5. A1363
6. A1365
7. A1367

Please refer to“'rohs'是什么意思？”发现在Quality and Environment FAQ。

Please refer to theQuality and Environment FAQ。

导航到质量标准和环境认证homepage on the Allegro website. In the section titled“Policies and Declarations”，有一个标题的声明和陈述部分。在这里，可以找到RoHS合规声明。