by Jochen Neller, Technical Expert Inductors at Rutronik.
In-house quartz crystal production reduces risk.
Supply chain disruptions have impacted quartz crystals, oscillators, and real- time clocks (RTCs), leading to shortages and longer delivery times. Suppliers with in-house production of these components have a clear advantage in terms of reliability and shorter delivery times.
Increasing reliability
One supplier that produces its quartz crystals in-house is Epson, ensuring availability and consistent quality. Epson focuses on SMDs for kHz quartz crystals available in small packages with welded metal covers. For the FC2012AN and FC3215AN series, Epson has been
able to lower the maximum equivalent series resistance (ESR) to 50kΩ, which counters the usual increase in ESR with smaller sizes.
MHz quartz crystals
Demand for MHz quartz crystals is increasing due to higher data transmission speeds. MHz quartz crystals are available in smaller packages (FA-128, FA-118T, and FA1210AN series) as development of this technology increases efficiency and minimizes costs. QMEMS, a wafer-based process, combines the high stability and precision of quartz crystals with MEMS technology for high performance in compact packages. The photolithographic process creates fine-structure oscillators with larger electrode areas and lower electrical resistance. Further processing using HFF technology ensures high mechanical stability with frequencies up to 500MHz.
Epson can deliver some series (e.g. FA-128, FC-12M, and FA-20H) in approximately 18 weeks despite market delivery times of two years or more for MHz quartz crystals.
SPXOs
Simple packaged crystal oscillators (SPXOs) are the simplest crystal oscillators without compensation or temperature control. They consist of a quartz crystal unit and an oscillating circuit.
For models that exhibit low jitter even at high frequencies, Epson uses quartz crystals as the fundamental wave oscillator in addition to low-noise oscillator ICs, either using HFF quartz crystals or with a PLL (phase-locked loop).
With this self-developed oscillator IC compensating for the frequency or temperature coefficient of the HFF quartz crystal, the SG2520 series achieves low phase noise and improved frequency stability of 25 ppm (SG2520_EGN/VGN) and 20 ppm (SG2520_ EHN/ VHN) at –40 to +125°C.
PLL technology allows programmable frequencies between 0.67MHz and 170MHz, enhancing availability by allowing modules to be set to specific frequencies. The SG-8018 series also has a low deviation of 50 ppm at –40
to +105°C, including aging stability over ten years. The SG-8101 series is even more accurate with a tolerance of 15 ppm, thanks to integrated temperature compensation.
TCXOs
Temperature-compensated crystal oscillators (TCXOs) are available for sensitive applications that require stable frequencies even with temperature fluctuations or over a wide temperature range. By providing its ICs, Epson can also produce the ASICs for its TCXOs and match the individual components, such as the control voltage generator, correction circuitry, and oscillator core. In addition to TCXOs with CMOS outputs, Epson’s portfolio includes those with clipped sine wave outputs, resulting in better EMI behavior. Offering high stability and low phase noise, the TG2016SxN and TG2025SxN series are ideal for use in wireless communication devices.
Supply chain disruptions, worsened by the 2020 fire at Asahi Kasei Microdevices, have affected SPXOs and TCXOs globally. Epson, with in-house developed ICs, has largely mitigated these effects and doubled production capacity, reducing delivery times to around 18 weeks (as of September 2022).
RTCs
Using oscillators allows for customized solutions but requires understanding individual components, leading to design errors and time-consuming corrections. Ready-made RTCs—like those offered by Epson— provide complete modules including quartz crystals, semiconductors, and other components for features like wakeup timer and timestamp. These RTCs reduce development time, space, and power consumption.