Silicon振荡器的电源去耦

Silicon振荡器的电源去耦，Silicon作为欧美元器件行业的佼佼者，一直以来通过自身的努力，持续不断为行业传递自身的价值，致力于帮助用户提供完美的解决方案为主，由于在晶体行业已有几十年的发展，对于洞察用户需求把控十分到位，总能凭着自身的见解，开发出大量适合市场发展的优质产品，好比高质量的有源晶振也是其主推的产品之一，并为赢得更多的关注度。

From time to time we are asked to recommend solutions for power supply decoupling and layout. This application note will address these questions by providing solutions which have provided good results and warnings regarding solutions which could produce undesirable results. 

我们不时被要求推荐电源去耦和布局的解决方案。这申请说明将通过提供具有良好效果的解决方案来解决这些问题关于可能产生不良结果的解决方案的警告。

Silicon’ oscillators are designed and tested to meet the highest standards of quality and performance. Our oscillators will meet their specifications over variations in power supply voltage and temperature. However, noise at the oscillator’s power supply input can degrade jitter and phase noise performance. To get the best performance possible, it is desirable to de-couple high frequency components from the power supply prior to the oscillator.  

Silicon的SMD振荡器经过设计和测试，以达到最高的质量和性能标准。随着电源电压和温度的变化，我们的振荡器将满足其规格。然而，振荡器电源输入处的噪声会降低抖动和相位噪声性能。到为了获得尽可能好的性能，最好将电源中的高频分量解耦在振荡器之前提供。
Power supply bypass design starts with low impedance power and ground connections. This is best provided by a multi-layer PWB incorporating internal power and ground planes. Bulk power supply bypass capacitance is included to reduce power supply ripple and improve the power supply’s surge capacity. Bulk bypass capacitance may exist anywhere on the target application board. 

电源旁路设计从低阻抗电源和接地连接开始。这最好由包含内部电源和接地平面的多层PWB来提供。大容量电源旁路包括电容以减少电源纹波并提高电源的浪涌容量。大容量旁路电容可能存在于目标应用板上的任何位置。
Unlike the bulk bypass capacitance, the oscillator’s high frequency bypass capacitors are placed as close as possible to the oscillator. Figure 1 shows typical bypass configuration for Silicon’ oscillators. The capacitance values shown in Figure-1 may be used for all product families. 

与大容量旁路电容不同，振荡器的高频旁路电容器放置得尽可能接近尽可能地连接到振荡器。图1显示了Silicon振荡器的典型旁路配置。这个图1所示的电容值可用于所有产品系列

A bit of comment needs to be added about capacitors. EIA specifies capacitors in four classes. Class-I are the most stable and includes the zero temperature coefficient NPO capacitors used for load capacitors in discrete crystal applications. Class-IV is specified but not commonly available. Class-II and Class-III are the most commonly used. For oscillator bypass applications, Silicon recommends at least X5R capacitors. This class of capacitor is specified from -55ºC to +80ºC, has excellent drift characteristics over this temperature range, excellent high frequency characteristics and good volumetric efficiency. Table 1 summarizes the characteristics of common EIA Class-II and Class-III capacitors. 

关于电容器，需要补充一点评论。EIA规定电容器分为四类。I类最稳定的，并且包括用于离散晶体应用中的负载电容器的零温度系数NPO电容器。IV类是指定的，但不常见。第二类和第三类是最常用的。对于有源晶体振荡器旁路应用，Silicon建议至少使用X5R电容器。该类电容器的温度范围为-55ºC至+80ºC，在该温度范围内具有优异的漂移特性、优异的高频特性和良好的体积效率。表1总结了普通EIA II级和III级电容器的特性。

表1电容器特性

In addition to the bypass capacitor network shown in Figure 1, some designers also insert a series impedance between the oscillator and power supply to create a low pass filter, further isolating the oscillator. The cutoff frequency for this simple filter is given by

除了图1所示的旁路电容器网络外，一些设计师还插入了串联阻抗在振荡器和电源之间创建低通滤波器，进一步隔离振荡器。截止日期这个简单滤波器的频率由下式给出：

The added impedance, either resistive or inductive, may be in series with the normal capacitive bypass network, or placed between the two bypass capacitors. These connections are shown in Figure 2. 

增加的阻抗，电阻或电感，可以与正常的电容旁路网络串联，或者放置在两个旁路电容器之间。这些连接如图2所示。Silicon振荡器的电源去耦.

Care must be taken any time a resistor is placed in series with the power supply. A surprisingly small value of resistance in series with the power supply is sufficient to reduce VCC below the oscillator’s VCCmin. Maximum current values for Silicon oscillators are specified in the data sheets and range from 5uA for some of our 32.768KHz real-time-clock oscillators to 90mA for higher frequency LVPECL oscillators. Table 2 provides maximum resistor values for combinations of ICC, VCC and power supply tolerance. 

电阻器与电源串联时必须小心。值小得惊人与电源串联的电阻足以将VCC降低到振荡器的VCCmin以下。最大限度Silicon石英晶体振荡器的电流值在数据表中有规定，我们的一些振荡器的电流范围为5uA32.768KHz实时时钟振荡器到90mA，用于更高频率的LVPECL振荡器。表2提供ICC、VCC和电源容差组合的最大电阻值。

Inserting a series ferrite bead between the power supply and the oscillator is also acceptable. The designer should select a low-Q, non-resonant ferrite bead (also called lossy or absorptive beads). A high-Q ferrite bead or inductor could create a resonant tank with the bypass and parasitic capacitance. When selecting a ferrite bead for this application, the bead’s DC resistance must be considered. It is not uncommon for the DC resistance to be one-Ohm or greater. 

在电源和振荡器之间插入串联铁氧体磁珠也是可以接受的。设计师应选择低Q、非谐振铁氧体磁珠（也称为损耗或吸收磁珠）。一种高Q铁氧体磁珠或电感器可以产生具有旁路和寄生电容的谐振回路。当选择铁氧体磁珠在这种应用中，必须考虑磁珠的直流电阻。DC并不罕见电阻为1欧姆或更大。
Lead lengths and PWB layout are important considerations for optimal performance. Figure 3 shows close spacing's, use of ground planes and parallel capacitor decoupling.

引线长度和PWB布局是优化性能的重要考虑因素。图3显示关闭间距、接地平面的使用和并联电容器去耦。