ECS時鐘晶體振蕩器ECS-3953M-080-B-TR適用于6G光通信，ECS公司從默默無名小型企業(yè)到如今知名品牌，一路走來傾盡無數(shù)的風(fēng)雨，通過自身的努力實現(xiàn)自我的價值，秉持著創(chuàng)新的設(shè)計理念，以及獨特化的見解，為行業(yè)持續(xù)貢獻(xiàn)自我的價值，以滿足各個領(lǐng)域的需求，隨著自身的切合實際情況進(jìn)行深入探究，發(fā)現(xiàn)品質(zhì)過硬的產(chǎn)品，永遠(yuǎn)是市場的最大需求，與此同時發(fā)布時鐘晶體振蕩器編碼ECS-3953M-080-B-TR，型號ECS-3953M，尺寸為7.50mmx5.00mm，頻率為8MHZ，ECS- 3951m (5V)和ECS 3953M (3.3V)系列是微型、晶體控制、小電流時鐘振蕩器陶瓷SMD封裝。包裝與金屬蓋接縫焊接。低姿態(tài)的包是理想的今天的先進(jìn)便攜式PC和儀表設(shè)計。
產(chǎn)品特性：3.3或5.0V版本，低功耗，待機(jī)功能，縫焊封裝，磁帶和卷軸(1,000個)，符合PbFree/RoHS標(biāo)準(zhǔn).

ECS Inc .堅信，無論所用產(chǎn)品的質(zhì)量如何，任何應(yīng)用程序都取決于其設(shè)計。ECS Inc .提供一些業(yè)界最好的頻率控制電子元件和石英晶體產(chǎn)品，它知道這些產(chǎn)品只是一個更大難題的開始。

The purpose of these application notes is to help customers in specifying clock oscillators. Background information about the type of oscillators offered by ECS is included along with some common definitions and helpful formulas. The ECS oscillator product line consists of clock oscillators, TCXOs, VCXOs, VCTCXOs, and VCOs.

The standard clock oscillator is the most common type of oscillator used and has applications in virtually every aspect of the electronics industry. The clock oscillator is used to establish a reference frequency used for timing purposes. A typical application is the sequencing of events in a computer.

A crystal controlled clock oscillator typically consists of an amplifier and a feedback network that selects a part of the amplifier output and returns it to the amplifier input. A simplified block diagram of such a circuit is shown below in (Fig 1).

Figure 1) Simplified Block Diagram of a Crystal Controlled Clock Oscillator

The basic criteria for oscillation in an oscillator are: 1. The open loop gain must be greater than the losses around the oscillator loop and 2. The phase shift around the oscillator loop must be either 0 or 360 degrees.

An oscillator can be used to generate different types of waveforms. The most common types of waveforms produced by an oscillator are sinusoidal and square.

The main parameters used in specifying a clock oscillator are listed below.

Logic TTL, HCMOS:In general, an HCMOS oscillator with drive TTL circuitry (not vice versa). The industry is moving away from the TTL logic as IC manufacturers are discontinuing the supply for many common TTL IC’s. Most ECS clock oscillators are HCMOS/TTL compatible.

Frequency Stability:The most common stabilities are 25, 50 and 100 PPM. Overall stability usually includes accuracy at 25°C, effects due to changes in operating temperature, input voltage, aging, shock and vibration. The ± 100PPM stability has been the most popular as it is sufficient to run microprocessors. The telecommunications industry has been moving toward tighter and tighter stabilities. Stabilities beyond ± 100PPM are no longer offered in commercial (0-70°C) applications, since standard process controls achieve this stability as a minimum. Requesting 50 PPM is usually a little more expensive. Clock oscillators requiring 25 PPM can significantly affect the price. For tighter than 25 PPM stability applications, please consult the factory or consider a TCXO.

TCXOs (Temperature Compensated Crystal Oscillators)

Typically consist of tight tolerance quartz crystal, a temperature compensation network, an oscillator circuit and a variety of buffer and/or output stages determined by the output requirement. The crystal has a characteristic of changing frequency when a capacitor is inserted in series with the crystal unit as shown in (Fig. 2)

Figure 2) Load Capacitance Characteristics of Crystal Unit

Utilizing the above characteristics, frequency can be stabilized by inserting a temperature compensation circuit consisting of thermistors, resistors and capacitors in the oscillation look as shown in (Fig. 3). The temperature compensation network is used to sense the ambient temperature and “pull” the crystal frequency in a manner which reduces frequency vs. temperature effect of the quartz crystal.

Figure 3) Temperature Compensation Circuit

A TCXO is generally required when overall stability needs are greater than those of a clock oscillator. Also, the long-term aging effects of a TCXO are better than those of most clock oscillators.

Input Voltage:Most TCXOs are designed to operate at 5VDC, 3.3 VDC or a combination of both.

RF Output:A TCXO can be manufactured with various types of outputs: sine wave, clipped sine wave, TTL, HCMOS and ECL. Be sure to specify the desired output type, signal requirements and the load that the oscillator will be driving.ECS時鐘晶體振蕩器ECS-3953M-080-B-TR適用于6G光通信.

TCXOs also have a frequency adjustment feature which allow for readjustment of the oscillator to its center frequency to compensate for aging. This adjustment can be provided in the following ways.

1. A mechanical adjustment (internal trimmer) within the oscillator accessible via hole in the enclosure.
2. An electrical adjustment via a lead in the enclosure for either a remotely located potentiometer or a voltage. An oscillator using this technique is called a Temperature Compensated Voltage Controlled Crystal Oscillator or TCVCXO.
3. A combination of both mechanical and electrical adjustment.

VCXOs (Voltage Controlled Crystal Oscillator)are crystals controlled oscillators in which the output frequency can be adjusted by varying the external control voltage across a variable capacitor ( varactor diode) within the oscillator circuit. The associated change in frequency due to the change in control voltage is known as pullability. VCXOs are used widely in telecommunications, instrumentation and other electronic equipment where a stable but electrically tunable oscillator is required.

The varactor diode is a semiconductor device that is designed to act as a variable capacitor when a voltage is applied to it. When used in series with crystal, as shown in (Fig. 4), changing the control voltage causes diode capacitance to change. This change in capacitance causes the total crystal load capacitance to change and subsequently causes a change in crystal frequency.

這些應(yīng)用筆記的目的是幫助客戶指定時鐘振蕩器。ECS提供的有關(guān)振蕩器類型的背景信息，以及一些常見的定義和有用的公式。ECS振蕩器產(chǎn)品線包括時鐘振蕩器、TCXOs、VCXOs、VCTCXOs和VCO。

什么是時鐘振蕩器？

標(biāo)準(zhǔn)時鐘振蕩器是最常用的振蕩器類型，幾乎在電子工業(yè)的每個方面都有應(yīng)用。時鐘振蕩器用于建立用于計時目的的參考頻率。一個典型的應(yīng)用是計算機(jī)中事件的排序。

晶體控制時鐘振蕩器通常由一個放大器和一個反饋網(wǎng)絡(luò)組成，該反饋網(wǎng)絡(luò)選擇放大器輸出的一部分，并將其返回到放大器輸入。這種電路的簡化框圖如下所示(圖1)。

圖1)晶體控制時鐘振蕩器的簡化框圖

振蕩器中振蕩的基本準(zhǔn)則是:1 .開環(huán)增益必須大于有源振蕩器環(huán)路周圍的損耗。振蕩器環(huán)路周圍的相移必須為0度或360度。

振蕩器可以用來產(chǎn)生不同類型的波形。振蕩器產(chǎn)生的最常見的波形類型是正弦波和方波。

下面列出了用于指定時鐘振蕩器的主要參數(shù)。

邏輯TTL，HCMOS:一般來說，HCMOS振蕩器具有驅(qū)動TTL電路(反之亦然)。隨著集成電路制造商停止供應(yīng)許多常見的TTL集成電路，業(yè)界正在遠(yuǎn)離TTL邏輯。大多數(shù)ECS時鐘振蕩器都是HCMOS/TTL兼容的。

頻率穩(wěn)定性:最常見的穩(wěn)定性是25、50和100 PPM。整體穩(wěn)定性通常包括25°C時的精度、工作溫度變化、輸入電壓、老化、沖擊和振動的影響。100PPM的穩(wěn)定性最受歡迎，因為它足以運行微處理器。電信行業(yè)正朝著越來越穩(wěn)定的方向發(fā)展。在商業(yè)(0-70°C)應(yīng)用中，不再提供超過100PPM的穩(wěn)定性，因為標(biāo)準(zhǔn)過程控制至少可以達(dá)到這種穩(wěn)定性。要求50 PPM通常會貴一點。要求25PPM的時鐘振蕩器會顯著影響價格。對于小于25 PPM的穩(wěn)定性應(yīng)用，請咨詢工廠或考慮TCXO。

溫度補(bǔ)償晶體振蕩器

通常由緊公差石英晶體、溫度補(bǔ)償網(wǎng)絡(luò)、振蕩器電路和由輸出要求確定的各種緩沖器和/或輸出級組成。當(dāng)電容器與晶體單元串聯(lián)插入時，晶體具有改變頻率的特性，如圖2所示

圖2)晶體單元的負(fù)載電容特性

利用上述特性，可以通過在振蕩電路中插入由熱敏電阻、電阻和電容組成的溫度補(bǔ)償電路來穩(wěn)定頻率，如圖3所示。溫度補(bǔ)償網(wǎng)絡(luò)用于檢測環(huán)境溫度，并以降低石英晶振的頻率溫度效應(yīng)的方式“牽引”晶體頻率。

圖3)溫度補(bǔ)償電路

當(dāng)整體穩(wěn)定性需求高于時鐘振蕩器時，通常需要TCXO。此外，TCXO的長期老化效果優(yōu)于大多數(shù)時鐘振蕩器。

輸入電壓:大多數(shù)TCXOs設(shè)計為在5VDC、3.3 VDC或兩者的組合下工作。

射頻輸出:TCXO可以制造各種類型的輸出:正弦波，削波正弦波，TTL，HCMOS和ECL。務(wù)必指定所需的輸出類型、信號要求和振蕩器將驅(qū)動的負(fù)載。

TCXOs還具有頻率調(diào)整功能，允許將振蕩器重新調(diào)整到其中心頻率，以補(bǔ)償老化。這種調(diào)整可以通過以下方式提供。

1. 有源晶體振蕩器內(nèi)的機(jī)械調(diào)節(jié)器(內(nèi)部微調(diào)器),可通過外殼上的孔接近。
2. 通過外殼中的導(dǎo)線對遠(yuǎn)程電位計或電壓進(jìn)行電氣調(diào)節(jié)。使用這種技術(shù)的振蕩器稱為溫度補(bǔ)償壓控晶體振蕩器或TCVCXO。
3. 機(jī)械和電氣調(diào)節(jié)的組合。

VCXOs(壓控晶體振蕩器)是晶體控制振蕩器，其中可以通過改變振蕩器電路內(nèi)可變電容器(變?nèi)荻O管)兩端的外部控制電壓來調(diào)整輸出頻率。由控制電壓變化引起的相關(guān)頻率變化稱為牽拉能力。VCXOs廣泛應(yīng)用于電信、儀器儀表和其他需要穩(wěn)定但電可調(diào)振蕩器的電子設(shè)備中。