如今，沒有石英晶振的圣誕節(jié)是不可想象的！為什么？即使是現(xiàn)代的戶外照明時(shí)間開關(guān)也需要石英來獲得準(zhǔn)確的時(shí)間基準(zhǔn)。此外，我們的許多禮物都是基于最先進(jìn)的電子產(chǎn)品。手機(jī)、智能手表、個(gè)人電腦——它們都需要高精度的頻率給定元件來相互通信。如果沒有這種交流，它們的用處就會受到嚴(yán)重限制，甚至不存在。這些設(shè)備通常從石英接收必要的驅(qū)動節(jié)奏，石英是這種設(shè)備的現(xiàn)代“心臟”。

Jauch Quartz的頻率給定組件工程師Mathias Laskus解釋說:“振蕩晶體會隨著溫度的變化而改變其行為和電氣特性。因此，溫度變化會導(dǎo)致頻率偏差。這種偏差以“百萬分之幾(ppm)”來衡量，這意味著:

1ppm =百萬分之一= 0.000001 = 0.0001%。

MHz范圍內(nèi)的振蕩貼片石英晶體也稱為AT切割晶體。它們包含薄石英晶片，即所謂的石英坯。at切割石英坯是以35°的AT角從石英塊上切割下來的。坯件的厚度基本上決定了室溫下的基頻。然而，石英坯從石英塊上切割下來的準(zhǔn)確角度是造成其他溫度下頻率偏差的原因。如果在切割過程中非常精確地達(dá)到35° 15′的理想角度，石英對溫度的敏感度就會降低。

您可以看到不同的切割角度選項(xiàng)。

溫度靈敏度是三次拋物線的函數(shù)。在切割過程中，即使是單角秒范圍內(nèi)的最小誤差也會導(dǎo)致曲線圍繞拐點(diǎn)旋轉(zhuǎn)。這惡化了后續(xù)應(yīng)用所需溫度范圍內(nèi)的溫度靈敏度。在坯件的制造過程中，由于可能的最大制造精度，完美的切割角度只能在有限的范圍內(nèi)實(shí)現(xiàn)。因此，制造的毛坯必須根據(jù)它們的偏差進(jìn)行分類，并根據(jù)它們的精度用于合適的晶體。法國JAUCH石英晶體溫度解說.

音叉晶體的溫度依賴性

對于音叉石英晶體(也稱為時(shí)鐘石英晶體)，倒拋物線的函數(shù)描述了頻率的溫度依賴性。在這種情況下，溫度相關(guān)頻率偏差為0ppm時(shí)的拋物線頂點(diǎn)在25°c，在較低和較高的溫度下，例如在該點(diǎn)的左側(cè)和右側(cè)，頻率逐漸下降，并且符合二次曲線。如果電路中的石英調(diào)整正確，將會有一個(gè)與溫度相關(guān)的滯后，例如實(shí)時(shí)時(shí)鐘。應(yīng)用程序的開發(fā)人員一定要考慮到這一點(diǎn)。

這對應(yīng)用程序意味著什么？

兩條溫度曲線都表明極端溫度對石英晶體的頻率有影響。對于大多數(shù)應(yīng)用而言，與溫度相關(guān)的微小頻率變化(例如-40°C至+85°C范圍內(nèi)的+/-15ppm)不成問題。然而，如果需要更精確的頻率，建議使用溫度補(bǔ)償晶體振蕩器，稱為TCXO。這提供了非常高的頻率精度，即使在很寬的溫度范圍內(nèi)也能達(dá)到幾個(gè)ppm。

我們很樂意為您的應(yīng)用選擇合適的時(shí)鐘發(fā)生器提供建議。

Nowadays, Christmas without quartz crystals is unimaginable! Why? Even the modern time switches for outdoor lighting need a quartz to have an accurate time base. Also, a lot of our gifts are based on state-of-the-art electronics. Cell phones, smartwatches, PCs – they all need highly accurate frequency giving components to communicate with each other. Without this communication, their usefulness is severely limited, or even non-existent. The devices usually receive the necessary driving rhythm from a quartz, the modern “heart” of such a device.

“Oscillating crystals change their behavior and electrical properties as a function of temperature,” explains Mathias Laskus, engineer for frequency giving components at Jauch Quartz. Hence, temperature changes lead to frequency deviations. This deviation is measured in “parts per million (ppm)” – which means:

1ppm = 1 part per million = 0.000001 = 0.0001%.

The temperature sensitivity of AT-cut crystals

The temperature sensitivity runs as a function of a cubic parabola. During cutting, even minimal inaccuracies in the range of single angular seconds lead to a rotation of the curve around the inflection point. This worsens the temperature sensitivity in the desired temperature range for the subsequent application. During the manufacturing process of the blanks, the perfect cutting angle can only be achieved to a limited extent due to the possible maximum manufacturing accuracy. Therefore, the manufactured blanks must be sorted according to their deviation and used for the appropriate crystals according to their accuracy.

Temperature dependence of tuning fork crystals

For tuning fork quartz crystals (also called clock quartz crystals) the function of an inverted parabola describes the temperature dependence of the frequency. The vertex of the parabola at a temperature-dependent frequency deviation of 0 ppm is in this case at 25 °C. At lower and at higher temperatures, for example to the left and to the right of this point, the frequency falls increasingly – and according to a quadratic curve. If the quartz in the circuit is correctly adjusted, there will be a temperature-related lag, for example with a RealTimeClock. The developer of an application must definitely take this into account.

What does this mean for the application?

Both temperature curves show that extreme temperatures have an influence on the frequency of quartz crystals. For the majority of applications, a slight temperature-related change in frequency, for example of +/-15 ppm in the range from -40 °C to +85 °C, is not a problem. However, if a more accurate frequency is required, it is recommended to use a temperature compensated crystal oscillator, called TCXO. This provides a very high frequency accuracy in the range of a few ppm even over wide temperature ranges.

We will be happy to advise you on the selection of the right clock generator for your application.