常见问答

信号完整性

EMI

Samtec连接器是否符合FCC B类EMI要求？

联邦要求（FCC 47 CFR Part 15、EN55022等）要求对计算机等有源电子系统进行EMI一致性测试。虽然无源元件可能会影响整个系统级EMI性能，但无法直接测试连接器、电缆组件、电阻器或螺栓是否符合EMI要求。

带护罩连接器和电缆组件是否有助于减少排放并提高电子产品的抗扰度？

是的，它们很有帮助，在某些情况下，帮助是极其显著的。具有周期性切换的信号（如时钟线）是典型的噪声源。如果将来自此类来源的电源耦合到离开带护罩外壳的电缆，则电缆可以像手机天线辐射那样辐射耦合的噪声（尽管效率不高）。在电缆上放置屏蔽（并正确端接屏蔽）可以显着减少辐射。除了辐射发射发生在外壳内部，对于外壳内的板到板连接器，情况都类似，因此在EMI测试期间可能会或可能不会看到辐射发射。

与Q Series™产品相比，Q2™产品有多大的屏蔽程度？

测试显示，在来自4-10 GHz的1-4 GHz和0-10 dB的频率范围内，有10-20 dB的提升。这是一个比较测试，其中带护罩连接器 (Q2™) 的辐射场与非屏蔽连接器 (Q Series™) 的辐射场进行比较。测试的关键意义是测试设置中及测试板上的所有变量，在两个测试中都需要相同。全波模拟显示在1-10 GHz频率范围内也有大约10 dB的提升。

使用板对板 (BTB) 连接器时，降低EMI的最佳做法是什么？

在我们回答这个问题之前，需要预先陈述一些假设：

• 我们正在解决开放式端子连接器，如Samtec QSE/QTE或SEAM/SEAF产品，而不是为BTB应用配置的同轴射频连接器。我们主要对kbps跨越到Gbps数据速率的数字应用感兴趣。我们无法解决非常低频的模拟（音频）类型应用。连接器是整个互连系统的一部分，可以包括印刷电路板 (PCB)。

了解BTB系统中的辐射机制或主要EMI天线是很重要的。一个很好的类比就是将PCB接地平面视为微带贴片天线的元件。在连接器上开发的任何纵向电压电位都显示为一个电压源，用于驱动PCB接地平面，这与驱动微带贴片天线的投料元件并无不同。这是一种有用的低频（50 MHz到100的MHz）近似值；在更高频率下，辐射系统更复杂，但最佳做法仍保持不变。

为了最大限度地减小连接器上的纵向电压电位，我们需要最大限度地减少信号返回路径的自偏电感。这里需要一些简短的术语定义：

• 环路电感是唯一“真实”或可测量的电感。自偏部分电感是一种有用的数学结构；它可以计算但不能直接测量。“自偏”意味着我们对仅从环路的一个导体产生的磁通量感兴趣。“部分”意味着我们只关注路径的一部分，特别是PCB之间的部分。

为了最大限度地减少连接器上的自偏分电感，需要遵循一些基本准则：

• 较短的BTB堆叠高度优于较高的BTB堆叠高度。通过将接地端子集成到信号端子磁场 (1:1) 中，最大限度地减小连接器中的环路面积。使用宽而扁平的导线进行信号返回，专用平面优于信号返回端子，使信号和接地摸具的特性阻抗尽可能低。

如果EMI是唯一的问题，BTB连接器应具有非常低的特性阻抗 (<1Ω)。信号和返回电流的平面分布在连接器上会有最低的自偏电感和最低的EMI。显然，这不是一个实用的准则，因为数据传输要求强制规定要与系统阻抗紧密匹配（通常为50Ω）。

适用于BTB连接器中EMI降低的相同物理特性也适用于PCB。信号返回路径的中断（例如接地平面中的分割）大大增加了返回路径的自偏部分电感，这可能会导致EMI问题。

电子设备的最佳EMI策略是考虑多个领域，如PCB设计（堆叠和电路布局）、连接器选择、信号返回管理（接地）、电源滤波（去耦/PI设计）和逻辑选择，重点是扩频时钟和边缘塑形。

电源完整性

If I am using a Samtec ECUE-12-XXX-T1-FF-XX-1-XX FireFly™ cable assembly, can I run auxiliary power through the twinax?

Auxiliary power is usually run through the PCB. The objective of a Flyover® cable assembly (such as the FireFly™ products) is to take the data off of the PCB to lessen the losses associated with the PCB and run the low-speed signals and power through the PCB. It is best practice to avoid running power through the twinax cables. If power must be run though the twinax cables, the power circuits must be very well bypassed and filtered at both ends. For more assistance, contact PowerIntegrity@samtec.com.

Additional considerations:

• Even if the power circuit is well bypassed and the current does not exceed the current capacity of the chosen conductor(s), the voltage drop has to be carefully checked. The TTF-36100 micro twinax cable specification says that the center conductor has approximately half an Ohm resistance for each foot length. The shield resistance is approximately three times lower. So for each foot of length and for each ampere of current, the voltage drop is 500 mV along the center conductor and 150 mV along the shield.
• The relatively high resistance of the shield that comes from the very small size means that the twinax cables lose shielding effectiveness up to higher frequencies (as opposed to bigger coax cables with heavy braid). As such, there is strong interaction among the twinax conductors below about one MHz, so if one carries power, any residual power noise at low frequencies will induce common-mode noise on the high-speed signals.

I am considering using a Samtec UDX6 connector. It has a block of high-speed pins and power blades in the same housing. How should I assign the power blades to different nets, what are the considerations?

In addition to the usual signal-integrity considerations, there are two potential interactions to consider related to the power blades: (1) how the pin and blade assignment impacts the power delivery and (2) signal-to-power crosstalk. For power delivery, the DC resistance (which determines the current carrying capacity) and the loop inductance matter most. The resistance also varies slightly with pin assignment. However, the inductance, which influences the transient response of the power path, will change significantly with blade assignment. When the inductance of the power delivery path matters for the application, we usually want to minimize it. The loop inductance formed by the blades is directly proportional to the size of the loop.

If the goal is to minimize loop inductance, we need to assign the power and power-return (or 'GND') blades in a pattern that forms the smallest possible loop size. This can be achieved by selecting adjacent blades for power and ground.

The crosstalk between power blades and high-speed signal pins also depends on the geometry of interacting power and signal loops. The interaction can be minimized by making the loops smaller, by placing them farther apart, or by forming orthogonal loops so that the magnetic coupling is minimized. If, in addition, we can also create the two loops such that the capacitive coupling also cancels, it will minimize the full electromagnetic coupling.

With multiple signal pins and power blades in the connector, there is no universal way to make use of crosstalk cancellation by orthogonal current loops, so we need to focus on minimizing loop size and placing them as far apart as we can.

In the high-speed block of pins, assigning signal and ground pins adjacent to each other is the accepted norm. In the power-blade section, assigning power and ground to adjacent blades will provide two benefits: as we saw above, it minimizes the power delivery inductance and it minimizes the crosstalk between power blades and signal pins.

And one last detail: the above considerations looked at circuit loops, when the signal, whether it is the high-speed signal or power noise, is considered differentially between the pins or blades. Sometimes common-mode noise is also important to minimize. It can be achieved by placing the pins and blades that are 'quieter' with respect to the ambient ground structure next to each other.

To read more on the subject, including pin and blade assignment illustrations, see Pin and Blade Assignment Considerations in Samtec UDX Connectors. For more assistance, contact PowerIntegrity@samtec.com.

Samtec是否有针对其电源完整性产品的测试程序？

是的。您可以点击此处找到电源测试标准白皮书的副本。

工作电压列在VAC中，但它在VDC中是什么？

直流额定值是来自AC额定值的正弦波峰值，即1.414乘以额定VAC。有关详情，请单击此处以查看我们的电源和电压额定值白皮书。

载流量是基于何种电压？

CCC适用于额定工作电压。

击穿电压、工作电压和DWV之间有什么区别？

击穿电压是连接器的故障点；工作电压是连接器应使用的最大连续电压；DWV是连接器的测试电压。

工作电压1/3为什么是DWV的1/3？

它的额定值为DWV的1/3，以考虑典型的浪涌和峰值，因此工作电压不会超过击穿电压。

您有哪些关于浪涌电压和浪涌电流的信息？

这些问题需要根据每个应用来回答。请联系我们的工程支持小组。

为什么一些载流量曲线在105°C终止，而其他载流量却在125°C终止？

锡端子机接口的额定温度为105°C，而金端子接口的额定温度为125°C。

Samtec如何测量载流量？

Samtec在端子的集中热点处进行测量，或使用校准的热电偶进行端子分组。点击此处查看我们实验室设置的照片。

通电的端子数量对载流量有多大的影响？

这个问题需要根据每个应用来回答。请联系我们的工程支持小组。

Samtec的产品是否符合爬电距离和电气间隙标准？

爬电距离和电气间隙要求根据实际应用会有很大差异，因此必须单独处理。有关爬电距离和电气间隙的更多信息，请联系Samtec的工程支持小组 (ESG)。

Samtec是否有特定的小组可以联系并询问有关电源连接器和/或测试的问题？

有关这类问题，请联系我们的工程支持小组。