A Micro-Packaged Linear Current Sensor IC

Primary conductor resistance of only 0.6 mΩ reduces power dissipation

肖恩·米兰
亚博棋牌游戏Allegro微系统有限责任公司

线性电流传感器ICACS711型，封装在一个0.75毫米厚的薄型封装中，尺寸仅为3毫米×3毫米！它是专为低压侧和小于100伏的传感应用需要5 A至30 A的连续电流传感。亚博尊贵会员

传统上，电流感测是通过感测电阻或电流互感器来完成的，这些电阻或电流互感器可以占用很大的PCB面积。从10到50兆欧的感测电阻值可以在更高的电流下消耗大量的功率，从而降低整个系统的效率，而电流互感器消耗大量的PCB不动产。霍尔效应传感器集成电路已被用来提供一种非接触的方法来测量导体中的电流，并提供与导体中的电流成比例的电压信号。

Allegro公司的新型电流传感器IC™ 微系统公司的ACS711（图1和图2）解决了尺寸问题，其占地面积非常小，3毫米乘3毫米，导体电阻仅为0.6兆欧，与典型的感测电阻运算放大器解决方案相比，其功耗降低了一个数量级。电流传感器集成电路的完全集成允许Allegro的工厂编程，提供更精确的解决方案，同时通过减少载流导体中的功率损耗提供小尺寸和更高效率的额外好处。

图1。ACS711 QFN封装尺寸，与美国。
10-cent coin

图2。具有QFN结构的ACS711设备：黄色为IC
芯片，红色是霍尔元件，绿色线代表磁通量，
and blue is the sensed current path

包装

Hall current sensor ICs with one turn and no magnetic core do not produce a large magnetic field, so placing the Hall sensing-element in close proximity to the sensed current is an attractive approach. The flux surrounding a conductor may be only a hundred gauss (10 mT) or less, and this diminishes rapidly with the distance of the Hall element from the conductor.

为了优化性能，ACS711设备采用Allegro专利倒装芯片磁场传感技术，如图2所示。倒装芯片的使用允许在硅表面上的集成电路的霍尔传感器部分（如图2中的红色方块所示）的活动区域被放置在最接近主导体的位置。这使得信号耦合良好。

采用经典的倒装芯片技术，与信号电路进行必要的连接，并将芯片支撑在引线框架上电流导体的上方。一次电流路径通过专利的暴露电流回路设计有效地传导到霍尔元件，终端直接焊接到PCB迹线。通过与导体如此紧密的磁耦合，信号灵敏度最大化，装置可以产生90 mV/A和45 mV/A，用于感测15 A和31 A满标度电流，传感器IC只需要3.3 V电源。

Flip-chip technology also allows case molding plastic to fill the small spaces between the primary current carrying conductor and both the die surface and the device signal leads, providing galvanic (voltage) isolation. With the attractive small dimensions of this device, the package provides isolation only to supply voltage values below mains line voltage. The ACS711 has been optimized for low voltage circuits, < 100 V, such as: 48 V solar circuits, communications, and consumer electronics and audio applications. The device is also economical to assemble into finished products and is excellent for low-side sensing applications in residential and commercial white goods appliances and with general-use motor drivers.

尽管ACS711的体积很小，但它可以在QFN封装中检测到相对较大的电流，高达±31 A。在更高的电流范围内，检测电阻器的功耗非常显著，在IC封装内外传导这种电流水平一直是传统的限制。QFN封装解决了这个问题，在安装表面上有两个大的焊盘，并且对初级感应电流传导回路的形状进行了仔细的分析。这种设计在封装中使用大量的铜导线来形成感应电流回路，而不需要连接线。QFN中的一次导体电阻仅为0.6mΩ，比低侧感测配置中使用的大多数感测电阻器小一个数量级。这降低了功耗，30 A时的典型功耗仅为0.54 W，15 A时的功耗仅为0.135 W。这不仅有助于提高系统效率，而且允许设备即使在高电流下也能保持冷却。如果客户在某些应用中更喜欢含铅封装，那么ACS711产品还提供SOIC-8配套封装。请访问Allegro网站www.wangzuanquan.com提供更多线性电流感应范围。亚博尊贵会员

焊接和热特性

Notwithstanding the low power dissipation, an even lower thermal resistance to ambient than that inherently provided by the relatively small, 3 mm²QFN package is required. Wide, highcurrent copper traces on the printed circuit board (PCB) are adequate to help cool the device, if designed properly. An example is shown in figure 3, the layout on the ACS711 prototyping board available from Allegro. Note that the two large pad areas, 4.5 mm across, are only slightly larger than the very small QFN package outline. On this board, two layers of 4 oz. copper are used, linked by thermal vias (those under the QFN can be filled or eliminated if necessary) to enhance thermal performance. The vias under the QFN can be filled or eliminated if necessary, as some customers find this difficult to accomplish in a production environment. Further design details and guidance for PCB mounting are available from Allegro.

图3。QFN电流传感器IC（Allegro）的PCB布局
board 85-0528)

Using the Allegro PCB of figure 3, temperature measurements were made across a range of sensed current levels. Figure 4 shows the results. The graph shows that at an ambient temperature of 85°C the sensor IC package can withstand 45 A continuous current before reaching the maximum recommended junction (die) temperature, 165°C. With proper PCB design, the device can be safely used in 30 A continuous-current applications at 85°C ambient temperature, with an approximately 50°C margin of safety before reaching a die temperature of 165°C.

图4。QFN的热力性能mounted on the PCB

设备特性、故障输出和精度

电压信号取决于电流的方向，可以测量交流和直流的双向电流。在零电流水平下，输出电压信号为电源电压的一半。

The ACS711 sensor IC also integrates a factory-programmed fast response digital fault output that has a 1.3 μs response time. It is set at 100% of the maximum current rating of the sensor IC. This fast fault signal can be used to prevent the destruction of IGBTs or other switching devices during short circuit or overcurrent conditions, or as a redundant fault feature in motor control applications.

Another inherent disadvantage of sense resistor with op-amp solutions is a reduction in accuracy with changes in temperature, because the sense resistor value changes. Hall-based sensor ICs are not subject to this error because the magnetic field generated by current flowing in a conductor is not temperature dependent. The Allegro ACS711 provides additional protection, against package thermal stress, through the application of an advanced Bi-CMOS process with built-in chopper circuitry to compensate for Hall element offset voltage changes. The fully integrated architecture of the ACS711 sensor IC further allows adjustment programming at Allegro end-of-line production testing to further reduce errors in gain and offset, delivering a more accurate sensing solution.

摘要

先进的Allegro专利倒装芯片封装线性霍尔集成电路已允许创建一个微型，3毫米×3毫米完全集成电流传感器设备，Allegro微系统ACS711，只有0.6兆欧的内阻，在一个封装，可以真正采取的热量。与适当的PCB设计一起使用，该设备可用于连续电流超过30A的应用，同时与现有的感测电阻器解决方案相比，功耗降低了一个数量级。亚博棋牌游戏亚博尊贵会员

Factory programming provides high accuracy in this IC, with an integrated fast response fault output. Together these techniques deliver the smallest current sensing footprint available for your application without compromising accuracy.

图5。ACS711的典型应用电路

本文件中包含的信息不构成Allegro就本文件主题向客户作出的任何陈述、保证、保证、担保或诱因。所提供的信息不能保证基于此信息的过程是可靠的，或者Allegro已经探索了所有可能的故障模式。客户有责任对最终产品进行充分的鉴定测试，以确保其可靠并满足所有设计要求。