直流和瞬态电流能力/保险丝特性of Surface Mount Current Sensor ICs
直流和瞬态电流能力/保险丝特性of Surface Mount Current Sensor ICs
Alex Latham和Scott Milne，
亚博棋牌游戏
介绍
Allegro MicroSystems offers a broad product family of current sensor IC solutions with integrated conductors. These products can be used to measure current in a variety of applications, including motor control, inverters, load detection and management, and overcurrent fault detection. For applications with normal operating currents up to 80 A, Allegro offers current sensor ICs in a number of standard surface-mount packages, such as SOIC-8, SOICW-16, QSOP-24, and QFN [1]. Due to their integrated conductors, these sensor ICs are placed in series with the current they are measuring. The integrated conductors are especially low resistance (1.2 mΩ down to less than 0.3 mΩ, depending on the package), so they generate very little heat under normal operating conditions. However, like all components that are in the current path, it is important to understand how they behave when subjected to currents above their rated nominal capability due to short circuits, inrush currents, or other transient conditions.
图1：传感器IC比较
Testing Performed and Limitations of Results
The focus of this study was on the SOIC-8, SOICW-16, and QFN-based current sensor ICs Allegro offers. It is important to note that the internal construction of these packages can vary from product to product, even though they use the same generic SOIC-8 or SOICW-16 footprint. Specifically, the packages and associated products tested are shown in Table 1.
| Package | 导线 | Product |
| SOIC-8型 | LC1: 1.2 mΩ | ACS711KLC |
| ACS712 | ||
| ACS713 | ||
| ACS714 | ||
| ACS715 | ||
| ACS724LLC公司 | ||
| ACS725LLC公司 | ||
| ACS730KLC公司 | ||
| ACS71240 | ||
| LC2: 0.65 mΩ | ACS722LLC公司 | |
| ACS723LLC | ||
| SOICW-16型 | LA: 1 mΩ | ACS710 |
| ACS716 | ||
| ACS720 | ||
| ACS732KLA型 | ||
| ACS733KLA型 | ||
| MA: 0.85 mΩ | ACS717 | |
| ACS718 | ||
| ACS722KMA | ||
| ACS723毫安 | ||
| ACS724毫安 | ||
| ACS725KMA | ||
| ACS732KMA型 |
||
| ACS733KMA |
||
| ACS71020型 | ||
| MC:0.265兆欧 | ACS724 |
Each package was subjected to the following tests:
| 大电流脉冲特性 (fuse characteristics) |
达到165°C模具温度与电流的时间 |
| Time to fuse the current conductor open vs. current | |
| DC Current Capability | 模具温度与直流电流和环境温度的关系 |
Unless otherwise stated, all data presented here was gathered at room temperature on products that were soldered to the product-specific demonstration boards developed by Allegro2. 散热特性，特别是在中等电流（<150 A）下，将根据电流传感器IC附近用于高电流记录道的PCB布局而变化。其他因素，例如PCBA是否用保形涂层封装（即，如果它是“封装的”）以及PCBA放置的外壳，都会影响系统的热特性。本研究的目的是比较和对比上述各种产品系列的相对性能，并大致了解每个包装能够承受的电流水平和持续时间。这些部件的高载流能力应在其使用的具体应用条件下进行验证。
Test Results
大电流脉冲特性（保险丝特性）
There are two different failure modes that can occur when Allegro’s integrated conductor current sensor ICs are exposed to high currents. Depending on the magnitude and duration of the current flowing through the conductor, either or both of the following failure modes can occur:
- The die can be damaged due to heat exposure, which can occur if the die is subjected to temperatures above165摄氏度。
- The primary conductor will act as a fuse and open.
图2显示了LC1封装（ACS712/3/4/5和ACS724/5设备）这些故障模式的时间与电流曲线。蓝色曲线表示导线保险丝断开的时间，黑色曲线表示模具达到165°C的时间。在中等电流（<150 A）下，这些传感器IC在熔断前会过热，这意味着在这些电流水平下，PCB布局和应用程序组装会对失效时间产生重大影响，因为它们可以帮助或阻碍热量从传感器IC流出。对于更高的电流瞬变（>150 A），传感器IC在模具过热之前倾向于熔断。这些事件的熔断时间主要取决于集成导体的尺寸和形状，不同应用的熔断时间差别较小。最终，应保持在安全操作区域内，低于熔合和过热曲线，图3显示了每个测试包的安全操作区域。
图2:LC1（SOIC-8）封装类型的保险丝和过温时间与电流
除了故障点之外，传感器集成电路熔断时的故障行为也很重要。一般来说，当集成导体熔断时，导体最薄的部分会碎裂，封装可能会破裂。在进行的所有测试中，当设备在过热前熔断时，故障不会导致设备的一次侧和二次侧之间出现任何短路。但是，如果包装损坏，设备的隔离等级将受到影响。
图3：安全操作区域-模具温度达到165°C或保险丝（以先发生者为准）与电流的时间。
同样重要的是要注意，如果在熔合前包裹过热，熔合事件将更加激烈。这些类型的故障发生在图2的浅灰色区域（超出安全操作区域），因为这是在熔合前使包装过热的地方。在这些情况下，存在显著的热量，在这些条件下，对任何过电流事件的反应都将更加强烈。图4显示了每个测试包的熔断时间，以供参考。但是，必须指出的是，零件只能在图2和图3所示的安全操作区域内操作。
图4：熔断时间-一次导线熔断所需的时间。
DC Current Capability
Similar to the differences in response to high current pulses of various magnitudes and durations, the same physical characteristics of the IC, PCB layout, and application assembly will impact the device’s ability to handle continuous currents and maintain die temperatures below 165°C. The other factor that will impact the part’s ability to safely carry large continuous currents is the ambient temperature. Figure 5 shows the temperature rise of the die vs. DC current for each of the packages tested. This can be added to the ambient temperature in order to determine the absolute die temperature, allowing one to determine the maximum allowable current for a given ambient temperature before the die goes beyond the absolute maximum of 165°C. For example, if the ambient temperature is 45°C and the continuous current through an ACS723LLC (LC2 package) is 50 A, the estimated die temperature inside the package would reach a steady state value of 115°C (45°C ambient temp + 70°C temperature rise).
图5：每种封装类型的芯片温度与电流的增加
Figure 6: Continuous Current vs. Ambient Temperature for Each Package Type
1对于需要亚博尊贵会员大于50 A的应用，请参阅50至400安培集成导体传感器集成电路for more information.
2Demo board Gerber files are available online in the Frequency Asked questions section of each sensor.