Welcome to the Epson SAW oscillator product training module. Epson has been providing their unique SAW oscillators that exhibit outstanding

Transcription

1 Welcome to the Epson SAW oscillator product training module. Epson has been providing their unique SAW oscillators that exhibit outstanding stability, ultra low jitter and the ability to oscillate at a high fundamental frequency for use in high capacity, high speed network systems. The purpose of this module is to educate about SAW oscillators, it advantages as well as provide an overview of Epson s SAW oscillator offerings. 1

2 The role of a timing device in electronic equipment is vital. A simply analogy is to compare it to the human body. If one thinks of a timing device as the heart, then the clock it outputs is the pulse, and the frequency the clock generates is the pulse count that feeds the ICs. With today high speed requirements, a clean and stable clock output is critical for system performance. Epson SAW oscillators serve this critical need. 2

3 A little background on the acronyms: Historically, in the US, military requirements have been the main impetus for research on crystal oscillators. The US Army sponsored most of the research, especially in the early days. According to folklore, the abbreviation XO instead of CO came about because, in the military, CO is the abbreviation for "commanding officer" and because "crystal" sounds a little like "xtal". The rest of this module will focus on SAW oscillators, although Epson offers all the other high end oscillator as well. 3

4 Surface Acoustic Wave (SAW) vibration only occurs on the surface of the quartz crystal chip allowing it to generate frequencies that ranges from several hundred MHz up to the GHz range. Bulk Acoustic Wave (BAW) associated AT type quartz crystal chip has the top surface and bottom surface of the crystal chip move in opposite directions allowing it to only cover frequencies ranging up to several hundred MHz. Epson SAW products line up includes SAW resonators, SAW filters and SAW oscillators. 4

5 A SAW oscillator has several technical advantages over the other type of high frequency type oscillators such as analog multiplier XO and PLL based XO. These advantages include high frequency oscillation with ultra low jitter and excellent phase noise performance while maintaining high reliability, which are discussed next in more detail. 5

6 A structure called Interdigital Transducer (IDT), with alternates positive and negative electrodes, is implemented on the surface of the quartz substrate so that a wave like vibration is emitted across the surface. The oscillation frequency is inherent in interval between electrodes (λ) and the propagation speed of sound (V) within the substrate. This type of quartz cut and structure is able to produce much higher frequencies than a tuning fork crystal or AT cut crystal. Like all of Epson s timing and sensor products, a quartz substrate is used for its piezo electric property, high reliability and stable characteristics over temperature. 6

7 Saw Oscillators are designed as ahigh frequency, high reliability, and high performance clock source used in many reference clock standards Some of the applications are, PCie, 1 Gigabit Ethernet, SAS/SATA, 10 Gigabit Ethernet standards and up to higher frequency applications in the order of 700MHz. The key advantages if a saw oscillator are: Fundamental frequency and no PLL: A clean clock source with no Spurs and does not exhibit frequency jumps High oscillation stability with Fundamental frequency: Unlike 3 rd overtone which can revert to fundamental mode during some voltage conditions, Fundamental frequency does not resonate in other modes. Low resonance impedance: Provides a better quality factor Q and therefore better phase noise. High Drive level resistance: Asaw oscillator keeps a stable clock even when it is exposed to excessive drive levels. 7

8 Epson Offers a wide range of SAW oscillator products. Our customers have the choice of cost, performance or size. The XG series SAW oscillator, such as XG 2102 or XG 2121 are designed for cost competitive purposes without sacrificing product performance. The EG 4100 series saw oscillator is designed for high stability. EG 4101CA and EG 4121CA can achieve a frequency tolerance of 25 ppm for frequencies between 100MHz to 700MHz. The EG 21xx series SAW oscillator uses our QMEMs technology to achieve a smaller package size such as 5mm by 3.2mm. 8

9 Since a SAW only operates on the surface of the quartz substrate and it oscillates at the fundamental mode, there are only harmonics of the carrier frequency and no sub harmonics nor spurious noise near the carrier frequency. 9

10 For AT crystals used in analog multiplier XO and PLL XO, spurious modes have different temperature coefficients compared to the carrier frequency s. There may not be any problems at 25C, but when the temperature or voltage change, the spurious mode may overlap with carrier frequency causing the frequency to dip ; this is called an activity dip. Since SAWs do not have spurious modes, activity dips and its associated problems are non existent, allowing for continuous oscillation with low jitter and excellent phase noise performance. 10

11 Here we have the comparison of the RMS and Peak to Peak jitter between an Epson s SAW oscillator, an analogmultiplier XO and a PLL based XO at MHz. Epson SAW oscillators have very low jitter, including deterministic, random and accumulated jitter, so designers can trust that their system will experience significantly reduced bit errors during data transmission. 11

12 Above is a phase noise comparison between an Epson s SAW oscillator, an analog multiplier XO and a PLL based XO at MHz. Epson SAW oscillators have excellent close in and noise floor characteristics since it can be driven with higher a drive level. The analog multiplier XO s noise floor has sub harmonics spikes while the PLL based XO s noise floor is greatly deteriorated by the PLL multiple of the spurious noise. The Epson SAW oscillator does not have sub harmonics nor spurious that affects the phase noise, and the structural reliability is not a not affected even with the higher drive level. 12

13 The SAW chip is much thicker than AT chips contributing to it s high reliability and ease of chip production. 13

14 Epson SAW oscillators interdigital transducer (IDT) are coated with a proprietary coating to prevent shorts due to particle contamination. Since Epson first introduced SAW oscillators in 1999, there has been zero reported oscillation failure to date (2013, present). 14

15 Above is technical summary comparison between Epson s SAW oscillator versus other types of high frequency type oscillators such as a competitor s SAW oscillators, analog multiplier XO and PLL based XO. The advantages of Epson s SAW oscillators are high frequency with low jitter, excellent phase noise and high reliability. 15

16 An important term to understand is frequency tolerance. Unlike a crystal unit where frequency tolerance is just the frequency deviation at 25C, for an oscillator the frequency tolerance is the overall frequency deviation which includes deviation at 25C, over the temperature range, reflow drift, supply voltage and output load. Epson s SAW oscillators have an option that includes frequency aging if needed. The common outputs are single ended like CMOS and differential outputs like LVDS, LVPECL and HCSL. Differential outputs are a newer technology and has many advantages including fast bit rates, low power consumption and good noise performance. 16

17 Jitter and Phase noise determines the accuracy or cleanness of the clock output. Jitter is simply the deviation of the actual clock from it s ideal position in time. It is measured in the time domain. Phase noise is the small fraction of undesirable energy near the output frequency due to internal and external environmental noise of the crystal and oscillation circuit. It is measured in the frequency domain. Low jitter and phase noise is essential for high speed data transmission applications, as discussed next. 17

18 These are examples of high speed applications that demand an accurate and clean frequency source. Epson has developed all the frequencies above for its SAW oscillators to serve these applications. 18

19 On Epson s website, one may find the recommended SAW oscillator categorized by the various features and functions of the associated application. Above is an example for the Network application. 19

20 Epson s website also has oscillation circuit design recommendations for common semiconductor products. For Xilinx for example, a designer can find out which SAW oscillator is recommended for a FPGA series and how to optimally design the interface. 20

21 Epson offers low jitter SAW oscillators in various package sizes, frequency ranges, tolerances, voltages and output types including CMOS and differential outputs like LVDS, LVPECL and HCSL. 21

22 The EG 2102CA and EG 2121CA have been serving high speed systems for many years. With the march towards faster communications, Epson continues to integrate value added features such as a HCSL differential output, tighter 48/52 duty and tight frequency tolerance over extended temperature that includes 10 years aging. 22

23 In summary, Epson s SAW oscillators offer several technical advantages over other types of high frequency type oscillators with its high fundamental frequency, low jitter, excellent phase noise and high reliability. These advantages are important components of stable, high capacity and high speed communications systems. Epson offers these low jitter SAW oscillators in various package sizes, frequency ranges, tolerances, voltages and output types including CMOS and differential outputs like LVDS, LVPECL and HCSL. Other features such as tighter frequency tolerance over industrial temperature, smaller size, lower current, lower jitter and lower phase noise are coming soon. Epson s SAW oscillators have an excellent track record for reliability and mass production and are a perfect match for current and next generation network communication systems. 23