Welding Inverter Circuit Diagram
Programmable Crystal Oscillators with Sub-ps Jitter and Multiple Frequency Capability
With an estimated market size for quartz devices at more than $ 2 billionand more than
Crystals delivered four billion annually, Professor Holton's Forecast overwhelming fulfilled.Crystals become not only the heart the telecommunication equipment, but also the electronic pulse in computers, printers, cameras, motor controllers, mobile phones and many other applications.
In 1939, the U.S. Army embarked on a path to adopt crystal control of radio communications. By providing robust wireless communications converted at precise frequencies Quartz crystals of the LC-tuned radio of the day in vital communication tools. With the war effort under way, the frequency control industry is experiencing amazing growth. Actually lived the crystal industry hand-to-mouth by material scarcity of quartz. Long production processes exaggerated and often unpredictable lead times assigned. Worse, reports began to high failure rates come back from the field. Late in 1943, the following telegram was received from the U.S. Army's Office of the Chief Signal Officer:
COMMUNICATIONS Eighth Air Force based in Great Britain
ANALYSIS OF LACK crystals cause CURE SAME
Of course, this creates a huge fault analysis Efforts of the army, with the result, diagnosis of an aging problem caused by contamination on the quartz surface. It was found that reliable operation of quartz crystals only if they are in clean, dry and hermetic packages is sealed.
Oscillator packages today are smaller, rates are close, and frequencies are higher. Nevertheless, quartz crystals are still in the same way that they were produced in 1943. Each new frequency requires a new section to be x-rayed crystal, lapped, mounted and sealed in the final package. In addition, the aging and reliability problems of the 8th Air Force in 1943 witnessed by new techniques exacerbated at higher frequencies by chemical thinning of quartz in the reverse mesa forms to achieve.
While programmable oscillators introduced in the 90s, offered the promise of strengthening the manufacturing process, the phase-locked loop (PLL) synthesis techniques used to generate as much jitter that they only useful, were in low-power applications.
And so, the quartz industry is largely the same manufacturing process of the 1940s strapped for producing of quartz oscillators. Each new frequency requires a new "Rock".
Implication Circuit architecture on hybrid Crystal Oscillator Manufacturing
As shown in Figure 1, the basic architecture of a quartz oscillator easily. Gain Block A stands for the preservation oscillator amplifier and block B is the feedback network with the crystal resonator.
The well-known Barkhausen criteria for oscillation is that if a frequency is present when the phase around the loop is zero, and the gain of a exceeds the loss of B, then swing the circuit at that frequency. The obvious conclusion with a narrow-band resonator like quartz, is that each new frequency requires a new crystal with the production of very profound consequences.
Thousands of different crystal frequencies necessary to support the variety of electronic systems in production today. The required temperature ranges and frequency rates are also variable, so the quartz bar cutting angle should also vary. Not only must the crystal thickness must be unique for each different frequency, but the angle of the cut from the quartz bar for other Order varied.
start with empty quartz production. If empty design changes are necessary because of difficulties encountered in the test phase, the process must when cutting to restart.
It only takes a typical quartz oscillator factory tour to see the amazing range of crystals in production at any given time. In addition to requiring long lead times difficult and often unpredictable, this build-to-order process implementation of modern manufacturing systems such as statistical quality control or continuous improvement. High-frequency fundamental (HFF) crystals for low-jitter clocks required to undergo additional chemical milling to achieve the blank quartz Thickness of ten microns, further compounding problems in the processing.
The situation is no less complicated for the SAW oscillators, where each new frequency requires A new wafer-mask can be developed. This requires CAD layout, mask making and wafer processing can be performed for each frequency.
It is quite an achievement, that the crystal was able to develop industrial production methods, with this huge product mix and the associated complex quartz processing.
A frequency-programmable Architecture for Low Jitter Clock Generation
In recent years, advances in fine line CMOS process technology enables IC designers to develop high-frequency PLL technology for use as a frequency agile clock multipliers and jitter attenuators in Multi-Giga bit per second optical networking applications. By using this technology, eliminated by a new class of hybrid oscillator, many of the complexities of manufacturing and performance issues traditionally associated with high-frequency resonators can be.
This new class of oscillator combines a fixed low-frequency crystal resonator with a new DSP-based PLL architecture known as DSPLL ®, as shown in Figure shown third The DSPLL is programmed to translate with a multiplication value, the fixed low-frequency crystal frequency to the desired output frequency. With this architecture, operating of high-frequency clocks to over 1 GHz with a jitter performance that is comparable to traditional high-voltage-controlled crystal oscillators (VCXO) and voltage-controlled SAW oscillators (VCSOs).
The engine was designed DSPLL with 1 ppb resolution over a tuning range spanning 10-945 MHz. Above 945 MHz, oscillator operation is limited choose bands to 1.4 GHz. All frequencies are synthesized from a fixed external crystal with a basic feedback oscillator topology. The crystal resonator does not need high Accuracy and must not be extendable as with all fine frequency tuning of the digital clock synthesis IC DSPLL performed. Non-volatile memory (NVM) is provided on-chip frequency synthesis to retain settings when the power supply is turned on.
A major advantage of this architecture is that a wide Range of low-jitter, high frequency clock signals can be generated from a conventional fixed frequency quartz overtone. This eliminates the need to clear HFF crystals or produce SAW resonators for each frequency. Besides the obvious by making the maintenance of a variety of different resonator frequencies a diverse set of customer requirements, HFF crystals and SAW resonators have support both reliability and performance issues that can be significantly improved by the new oscillator Architecture.
Hybrid Clock Module with a fixed frequency Crystal
The DSPLL clock synthesis IC is designed to achieve with a quartz crystal packaged in a hermetically sealed ceramic package housing both quartz oscillator support (Si530 XO) and voltage-controlled crystal oscillator (Si550 VCXO) applications. Figure 4 shows a block diagram of the Si550 VCXO hybrid technology involving DSPLL. A provision to enable or disable the output signal is determined by the OE pad available. A fixed frequency crystal, such as 120 MHz third harmonic in the ceramic, hermetically sealed, used hybrid module.
As with conventional hybrid XO and VCXO, high temperature, Co-fired ceramic (HTCC) is used for the package, and the lid sealed with seam sealing. Package hermeticity is better than 5×10-8 atm-cc /, such as helium leak test Fine confirmed. Industry-standard 7 x 5 mm package size and pad layout used for backward compatibility with existing oscillator.
Revolutionized Manufacturing Flow
A production flow, tailored for short lead times and process optimization as shown in Figure 6 is this is made possible by hybrid oscillators including the DSPLL clock synthesis IC. This trend is taking stock of "raw" unprogrammed oscillators produced by the hermetically DSPLL IC together with the low frequency crystal blank. While the hybrid assembly of the crystal blank and IC have some similarities to the river, There are two major simplifications. Initially, only a frequency of crystal blank is required, and secondly, the fine frequency tuning step eliminated. This allows continuous improvement of the design and hybrid assembly while eliminating an entire step.
In response customer orders, "raw" devices pulled from inventory, programmed to meet customer frequency specifications and shipped. Thus, the order processing flow changes from a complex build-to-order process with eight weeks lead time to a simple program-to-order process with one week delivery time. In addition to offering much shorter lead times, this method also facilitates modern techniques, such as lean manufacturing and continuous improvement.
Improved Initial Frequency Accuracy
Oscillator design with the DSPLL Clock IC eliminate high-resolution frequency synthesis of one of the largest variables that determines the initial accuracy of XO. Both traditional and hybrid crystals XO Experience a two-frequency adaptation process. The first step, the so-called base coat is in a batch mode with thin-film deposition techniques such as sputtering carried out. A Crystal monitor cooperation with institutions are to be plated, and the frequency is monitored as a measure of the layer thickness. Since the variation of the layer thickness slightly changing the vibrating mass, the frequency can be adjusted slightly by trimming the layer thickness. This technique is limited to within a few hundred ppm, a second Fine-tuning process is required. Fine tuning relates selectively adding or removing metal from the surface of the quartz and again changing the vibrating mass. The frequency is continuously monitored, and the process is completed when the target frequency is achieved. The process sensitivity is very difficult for HFF crystal oscillators. Since perform a single atomic layer of metal can adjust the frequency to change tens of pages, to achieve an initial tolerance of 10 ppm required deposit of less than an atomic monolayer. Unfortunately, the oscillator must be sealed, and the resulting change in parasitic capacitance caused additional changes in the Frequency. GFCI mechanical stresses in the package also cause frequency shifts. For HFF VCXOs initial accuracy can double-digit ppm. SAW oscillators are in a similar way by the ability of ultra-thin layers and residual stresses affected control package.
With the integration of high-resolution frequency synthesis in the DSPLL clock IC, the oscillator frequency is set by a simple programming step rather than the traditional two-step process tuning. In contrast, the specifications for the crystal resonator in DSPLL-based hybrid oscillators can be relaxed to an initial accuracy of ± 10,000. As a result, only the first baseplating of the crystal is necessary and fine-tuning step can be eliminated. In addition, moves to change the frequency by both parasitic capacitance and offset residual stress package may be because the oscillator frequency is programmed by the final sealing. Finally, because the DSPLL clock IC offers programming resolution of less ppb than one would expect that the first frequency is a ppm accuracy possible for high frequency XO and VCXO devices. This is about an order of magnitude better than conventional high-frequency oscillators.
Improved Aging Performance
Operation on a harmonic reduces the resonator C1 by the inverse of the squared harmonic. This means that a third overtone crystal is about one-ninth of the pull area of crucial importance, and a fifth harmonic is only one twenty-fifth of the pull area. While this is advantageous for high-stability OCXO, VCXO far, this is undesirable drag operation and essentially involves the use of Fundamental mode crystals. Achieving adequate pull range is the real reason behind the use of HFF crystals for VHF-band VCXOs, such as 155 MHz. It is known that the aging the inverse performance of quartz blank thickness (ie, a thick quartz blank have superior aging) is used. For example, a 38.8 MHz fundamental mode resonator have aging beyond that of a 155 MHz resonator. The 38.8 MHz fundamental is a third harmonic is resonant at 116.4 MHz. Since the oscillator is not pulled directly with the DSPLL architecture this resonator can be easily used in a VCXO using the Si5301 IC. Since the resonator thickness of a 116.4 MHz third overtone is four times the thickness of a 155 MHz fundamental, aging Performance can be improved similarly. Aging for the module is specified at ± 10 ppm over a typical 15-year life. This contrasts with typical SAW or HFF aging of several ppm / year.
Low jitter clock signals
Jitter clock signal is a critical parameter for many applications and is an important factor in determining key system attributes, such as bit-error rate (BER). Jitter is derived from an integration of phase noise over a certain range.
Phase noise at offsets below 10 kHz is primarily determined by the on-chip crystal oscillator, while the output LVPECL signal levels largely stopped the background noise for offset frequencies greater than 10 MHz. Intermediate frequency phase noise is determined by the on-chip VCO and associated PLL components. Jitter of integration Phase noise is derived 0.332 ps over the bandwidth of 12 kHz to 20 MHz and 0.319 ps over the bandwidth of 50 kHz to 80 MHz. This performance is essentially Performance Results usually get when using high-
SAW resonators or HFF in the conventional feedback oscillator topology Figure 1 Depending on the ratio of output frequencies to crystal resonator, some spurious signal content will be generated. For a given value of -80 dBc, spurious content is much lower than in the past in programmable Watches.
Programmable Tuning Slope
Traditional VCXOs utilize a varactor diode to the resonant frequency of the oscillation loop to change. Since the loop resonance frequency is known by the C1 / 2 (C0 + CL), where C1 and C0 are crystal equivalent circuit values and modified CL is the load capacitance changes the CL effect on the output frequency. Non-linear behavior in the oscillation loop determines the overall mood slope linearity. The mood of the slope, K, measured in ppm / V and C1 is directly proportional to the crystal movement capacity.
In contrast, the tuning voltage, Vc, at the DSPLL IC through a high-resolution digital ADC. The resulting digital number is used to modify slightly the frequency synthesis engine and thus the output frequency. Since Kv is simply a numerical multiplication factor, different values of Vc can be programmed to be built after the oscillator.
These results were from a single hybrid oscillator by simply reprogramming the value obtained Kv. With programmable gain ranges from 15 to 270 ppm / V, Kv effectively emulates typical characteristics of most SAW and crystal VCXO. The small roll-off at voltages is above 3 V by hanging light of the reference voltage for the ADC converter as Vc approaches VDD. Linearity, especially for the most useful range below 3V, is dramatically improved capacity to conventional diode-based VCXOs.
Multiple frequency operation of a Crystal Resonator
Applications are emerging that require multiple clock frequencies slightly offset from each other. For example, 622.08 MHz is a common SONET transport frequency. Forward Error Correction (FEC) is used to improve bit error rate performance, thus, additional bits are interleaved within the SONET payload. This increases the clock frequency at a slightly higher frequency, such as 666.5143 MHz. Conventional technology VCXOs must use different crystals or SAW resonators for each frequency. This approach is increasingly untenable as the number of required frequencies increases beyond two. With DSPLL clock synthesis, multiple output frequencies can be easily generated from a single resonator. With similar packing as in Figure 5, have dual-frequency XO (Si532) and VCXO (Si552) developed oscillator modules, two selectable output frequencies from a single offer Rock crystal. In the quad XO (Si534) and VCXO (Si554) series, additional pads on the ceramic package for binary selection of four individual output frequencies provided. Similar As with the dual-frequency parts, only one crystal is required, and the choice of output frequencies is arbitrary within the operating bandwidth of the DSPLL IC.
been a new class of quartz oscillators developed, offers high resolution, programmable frequency and high power. These oscillators dramatically simplify the Manufacturing process and thereby shorten product lead times. Additional benefits include better performance initial frequency accuracy, long-term aging and voltage control Linearity.