Differential Current Sensing with the 1 MHz Bandwidth ACS733
Differential Current Sensing with the 1 MHz Bandwidth ACS733
通过Maxwell Mcnally，Al雷竞技竞猜下载legro Microsystems，LLC
抽象的
本应用笔记描述了使用新的高度高带宽的使用ACS733Hall效应了Allegro Microsystems的电流传感器集成电路（IC），并通过高速电流互感器（CT）雷竞技竞猜下载电流检测解决方案来概述其特性和优点。
介绍
这ACS733是第1 MHz带宽霍尔效应电流传感器IC，3600 Vrms.isolation from Allegro. The sensor provides users with an accurate, low cost solution for isolated current sensing at high bandwidths with a small form factor. The device’s high bandwidth is accomplished by a high-speed analog signal path that employs differential sensing to provide immunity to interfering common mode magnetic fields. Figure 1 below shows the pinout of the device. The IC is packaged in the wide body SOIC 16 pin LA package. Pins 1 through 8 of the part are reserved for current input, four pins for both the positive and negative terminals. These pins are all internally connected with low resistance leadframe copper for better thermal performance.
引脚9到16的ACS733是输出信号引脚。VCC和GND用于为设备供电，VIOUT是表示IP总线上感测电流电平的模拟输出。这过错当感测到低量的电流时，引脚很高，但如果感测到上方的电流，则将拉低。该级别设置在VOC引脚上，电压划分为VCC的百分比，对应于设备的最大额定电流的百分比。程序引脚用于工厂校准，应将其绑定到地面，以便在应用中进行最佳ESD性能。
Differential Sensing
依赖于测量磁场的电流传感技术可能因外部磁场而受到损害。通过使用由输入电流产生的字段产生的相反极性的两个霍尔板，ACS733能够拒绝共模场。这允许TE部件在其他电流迹线附近使用。ACS733具有约-40dB的共模场抑制均匀和恒定的字段。有关差分传感的更多信息，请参阅应用笔记“Common Mode Field Rejection in Coreless Hall-Effect Current Sensor ICs“。
这common-mode field rejection of the ACS733 is an advantage over a CT, because a CT core can saturate in the presence of external magnetic field and change the operating characteristics of the device.
噪音和敏感性
这ACS733has a typical noise density of 80 μA/√Hz. Across the entire bandwidth of 1 MHz, this becomes an input-referred total noise of 100 mARMS. At different sensitivities, this amperage error will manifest at the output as different levels of mV error, but this indicates the part has an effective 100 mA resolution. Table 1 below compares the mV output error seen for the currently offered sensitivities of the ACS733. However, this noise can be reduced by decreasing the effective bandwidth of the device, either with oversampling and averaging, or by filtering the output with an RC filter.
表1：灵敏度和导致MV噪声
| Part | 灵敏度 （mv / a） |
噪声密度 (μA/√Hz) |
解析度 (mA) |
错误 (mV) |
| 733-20AB | 66 | 80 | 100. | 6.6 |
| 733-40AU | 4.4 | |||
| 733 - 40 - ab | 33 | 3.3 | ||
| 733-65AB | 20 | 2.0 |
高带宽操作和快速响应时间
这ACS733has a high operating bandwidth of 1 MHz. The device’s high speed analog signal path provides the fastest response time of any Allegro fully integrated current sensor IC. The typical response time to a step input is <800 ns on the output, and the typical fault output responds in <600 ns. Figure 3 shows the ACS733 responding to a current step compared to the response of a typical current transformer (CT). Both respond very quickly to the 1 μs input step.
User-Settable Overcurrent Fault Detection
额外的特征ACS733is the user-settable overcurrent open-drain NMOS fault output. This allows an even faster reporting of overcurrent or shorting events. This pin will detect overcurrent events faster than ADC conversion of the analog output signal. The fault level of the ACS733 can be set to any level from 50% of the maximum primary sensing current (IPR（MAX）），一直到200％的我PR（MAX）在VOC引脚上使用简单的电阻分压器。这为客户提供了一个简单的方法来为其特定应用程序设置过流级别。
VOC引脚上的电阻分压器设置为VCC的10％，将故障级别设置为50％公关(最大), and a voltage level of 40% of VCC to set the fault level at 200% of IPR（MAX）. Table 2 below shows these calculations for the ACS733 at four different fault levels. Equation 1 shows the calculation for the percent of VCC for any desired fault level.
VOCPercent=错误Percent×0.2（1）
Table 2: Fault Level and Voltage Divider Examples
| 供应 Voltage (V) |
VOC (%VCC) |
VOC (V) |
Fault Level （％IPR（MAX）） |
Resistors (kΩ) |
| 3.3 |
10 | 0.33 | 50 | 9/1 |
| 20 | 0.66 | 100. | 8/2 | |
| 30 | 0.99 | 150 | 7 / 3 | |
| 40 | 1.32 | 200. | 6 / 4 |
当检测到故障时，故障信号很高。发生过流事件时，开漏NMOS输出会拉动输出过错别针低。下面的图4显示了响应于电流步骤输入的故障输出的功能。由于该设备具有开放式NMOS输出，因此它们可以逻辑地或者用于多相系统到控制器的单个故障中断数字I / O引脚。
Compact Form Factor
A current transformer is bulky, requiring an offset core with windings and a resistive load to sense current. The ACS733 is a fully integrated sensing solution in a standard SOIC16W surface mount package that takes up minimal printed circuit board (PCB) area. Below, Figure 5 shows the size of the ACS733 compared to two CTs. When trying to minimize the size of a system, the ability to run the current trace on the board to the part which is mounted to the PCB would offer a significant space-saving advantage.
High Voltage Isolation
Despite its small size, the patented package technology provides for high voltage isolation. The high current pins are isolated from the low voltage signal pins because only the magnetic field needs to be sensed. The ACS733 in the SOIC16W (LA package) is certified to 3600 VRMS in accordance with UL 60950-1 (edition 2).
结论
这ACS733具有一系列功能，可在需要高速和高压隔离电流检测时具有显着的优势。LA SOICW包装是一种表面安装解决方案，易于集成并在庞大的电流互感器解决方案上减少PCB区域。ACS733的SOIC16宽体包提供3600 VRMS隔离，从电流承载迹线到信号销。传感器IC在Allegro工厂的工作温度范围内进行优化，并在发生过电流和短路事件时为快速数字输出提供开放式NMOS故障输出。这种完全集成的传感技术是真正的一种芯片解决方案，与汽车和工业应用兼容，使工程师易于设计入其应用。雷竞技最新网址