Crystek TCXO溫補晶振數(shù)據(jù)手冊，在偌大的市場之中，Crystek公司不斷調(diào)整自身的定位，經(jīng)過長期的積累，以及對于電子元器件行業(yè)的深度剖析，使得其能將目光移動到電信應(yīng)用，并針對性開發(fā)系列高品質(zhì)的有源晶體振蕩器，隨之為了凸顯產(chǎn)品的性能，開發(fā)新穎的TCXO溫補晶振，正是因為對于產(chǎn)品的不懈追求，Crystek才能不斷挑戰(zhàn)自我的極限，開發(fā)適合市場發(fā)展的優(yōu)質(zhì)產(chǎn)品.

溫度補償晶體振蕩器在今天的無線通信系統(tǒng)。它們已成為重要組成部分移動電話和不斷增長的無線PDA行業(yè)。高端TCXO也是電信和其他行業(yè)。

TCXO溫度補償晶體振蕩器和一個簡單的晶體振蕩器TCXO包含額外的校正（補償）電路晶體的頻率對溫度的特性。圖1描繪了關(guān)于水晶的簡單說明被校正。附加補償電路分為三個主要類別：數(shù)字、模擬或模擬/數(shù)字組合。了解差異數(shù)字和模擬之間的補償很重要，因為在某些情況下箱子，不能互換。

未補償頻率圖1所示的穩(wěn)定性是典型的AT切割石英晶體。它實際上是一組曲線，主要由切割晶體坯料的角度決定。這些曲線遵循形式為：

商品TCXO可從+/-在-40ºC至+85ºC范圍內(nèi)，1.5ppm至+/-5ppm頻率穩(wěn)定性最高標準規(guī)格為+/-2.5ppm以上-30ºC至+75ºC。頻率穩(wěn)定性在0ºC至+70ºC范圍內(nèi)低于+/-1.5ppm很難實現(xiàn)，因此跌倒進入高性能類別。商品TCXO晶振通常成本更低超過8美元，同時具有高性能TCXO通常為15美元或以上。
商品TCXO可以以非常小的包裝制造，例如5x3.2x1.5mm，甚至3.2x2.5x1mm更小的尺寸即將出現(xiàn)。這些微型振蕩器都是基于ASIC大批量生產(chǎn)。由于使用的特定ASIC，晶體振蕩器公司不能提供任何自定義（頻率除外）在家庭范圍內(nèi)。此外，所有這些小型TCXO實際上都是VCTCXO——也就是說，它們提供了用于電氣調(diào)諧或偏差的引腳。

圖3中的ADTCXO是目前在手機行業(yè)使用的型號，有5x3.2x1.5mm并且更小。這些振蕩器也是由于其體積小、成本低，被設(shè)計用于所有類型的設(shè)備費用但是，設(shè)計師要小心：圖3的DTCXO版本和其他數(shù)字實現(xiàn)，階段將發(fā)生命中（突然的相位變化）當振蕩器進行校正時因為它感應(yīng)到了溫度改變的ADTCXO版本圖3沒有相位跳躍由于其模擬后端。
確定振蕩器是否具有相位命中或頻率階躍可能不會在頻率與溫度的曲線中很容易看到。取頻率對溫度的一階導(dǎo)數(shù)數(shù)據(jù)可以幫助揭示階段命中率。查看階段命中率的另一種方法是使用正在使用的TCXO設(shè)置測試作為相位的參考頻率鎖相環(huán)（PLL），然后監(jiān)測相位檢測器上的錯誤電壓TCXO隨著溫度而傾斜。
一個大的相位命中可以解鎖許多如果不能吸收。因此，盡職調(diào)查必須由設(shè)計師提前完成考慮使用數(shù)字實現(xiàn)的振蕩器。
數(shù)控晶體此處未顯示振蕩器（DCXO）作為一個塊，因為它可以用許多不同的方式來實現(xiàn)。這個作者將DCXO定義為任何晶體振蕩器，其中晶體由設(shè)備的主機微處理器。修正情報可能如下：
1）Crystal的頻率與溫度曲線
2）來自外部來源的計時（即，小區(qū)站可以通過定時到PDA或手機）
3）來自外部或內(nèi)部來源
DCXO的設(shè)計者可能不會想要實現(xiàn)良好的穩(wěn)定性TCXO。例如，他或她可能滿足于將+/-25ppm晶體補償/校正為+/-5ppm而不增加獨立TCXO的成本。另一個優(yōu)點使用主微處理器執(zhí)行校正是指可以停止發(fā)送時的更新，以及可能在接收時。

表1總結(jié)了TCXO的不同版本以及簡單的時鐘（XO）和VCXO進行比較。

Temperature Compensated Crystal Oscillators (TCXOs) are widely used in today’s wireless communications systems. They have become a vital component to cell phones and the growing wireless PDA industry. High-end TCXOs are also an important component in telecom and other industries.

The major difference between a TCXO and a simple crystal oscillator is that the TCXO contains additional circuitry that corrects (compensates) the crystal’s frequency vs. temperature characteristics. Figure 1 depicts a simple illustration on how the crystal is corrected. The additional compensating circuitry falls into three major categories: Digital, Analog or Analog/Digital combination. Understanding the differences between digital and analog compensation is important since they, in some cases, are not interchangeable. 

The un-compensated frequency stability shown in Figure 1 is of a typical AT-cut quartz crystal. It is actually a family of curves determined primarily by the angle at which the crystal blank is cut. These curves follow a cubic equation of the form:

Commodity TCXOs are available from +/-1.5ppm to +/-5ppm frequency stability over -40ºC to +85ºC, with the most standard spec being +/-2.5ppm over -30ºC to +75ºC. Frequency stabilities below +/-1.5 ppm over 0ºC to +70ºC are difficult to achieve and hence fall into the high-performance category. Commodity TCXOs typically cost less than $8, while high-performance TCXOs are often $15 or more.

Commodity TCXOs can be manufactured in very small packages, such as 5x3.2x1.5mm and even 3.2x2.5x1mm with smaller sizes on the horizon. These tiny oscillators are all ASIC-based for high-volume manufacturing. Due to the specific ASIC being used, the crystal oscillator companies cannot offer any customization except for frequency within the range of the family. In addition, all these small TCXOs are actually VCTCXOs – that is, they provide a pin for electrical tuning or deviation. 

Output waveform options on these tiny TCXOs are limited to clipped-sine or sinewave only. If you need HCMOS, for example, it is available only on the larger packages. High performance TCXOs are available with all the popular waveform options(Sinewave, HCMOS, LVPECL, etc.).The clipped-sine waveform has one major advantage over the other waveforms: current draw. The typical current draw for clipped-sine is 2mA max at +3V. The internal clipped-sine driver is simply sourced from the collector of a bipolar transistor. This means that load seen by the oscillator has to be high impedance; typically it calls for a 10K Ohm load. The clipped-sine driver is perfect for driving PLL ICs directly providing a low current solution.
There are four digitally implemented (and one basic analog) types. These are as follows: 

TCXO – Temperature Compensated Crystal Oscillator (See Figure 2) 

ADTCXO – Analog Digital Temperature Compensated Crystal Oscillator (See Figure 3 with the exception that the DAC and Logic are replaced with a Cubic function and analog amplifiers respectively) 

 DTCXO – Digital Temperature Compensated Crystal Oscillator (See Figure 3)

 MCXO – Microprocessor Compensated Crystal Oscillator (See Figure 4) 

 DCXO – Digitally Controlled Crystal Oscillator

The ADTCXO in Figure 3 is the type now used in the cell phone industry and is available in 5x3.2x1.5mm and smaller. These oscillators are also being designed in all types of equipment due to their small size and low cost. But, designers beware: with the DTCXO version of Figure 3 and the other digital implementations, phase hits (abrupt phase changes) will occur when the oscillator makes a correction because it sensed a temperature change. The ADTCXO version of Figure 3 does not have phase jumps due to its analog back-end.

Determining if an oscillator has phase hits or frequency steps may not be easy to see in the frequency vs. temperature curve. Taking the first derivative of the frequency vs. temperature data can help reveal the phase hits. Another way to see the phase hits is to set up a test with the TCXO being used as the reference frequency to a phase locked loop (PLL), then monitor the error voltage on phase detector while the TCXO is ramped over temperature.

A large phase hit can un-lock many communication links if it cannot be absorbed. Therefore, due diligence must be done upfront by the designer considering using a digitally implemented oscillator.

The Digitally Controlled Crystal Oscillator (DCXO) is not shown here as a block because it can be implemented in many different ways. The author defines a DCXO as any crystal oscillator where the frequency of the crystal is corrected by the equipment’s host microprocessor. The correction intelligence may be the following: 

1) Crystal’s freq. vs. temp. curve 

2) Timing from an external source (i.e., a cell station can pass timing to the PDA or cell phone) 

3) Reference frequency from an external or internal source

The designer of a DCXO may not want to achieve the stability of a good TCXO. For example he or she might be satisfied with compensating/correcting a +/-25ppm crystal to +/-5ppm without adding the cost of a stand-alone TCXO. Another advantage to using the host microprocessor to perform corrections is that one can halt the update when transmitting, and
possibly while receiving.