Advances in Silicon Technology Enables Replacement
With a niche size estimated at beyond $650M and others than 0.4B crystal oscillators supplied annually, quartz crystal oscillators have long been the preferred choice for clock generation in consumer, computing, and communication software program. Quartz oscillators are to be found in a variety of frequencies, package sizes, and stabilities. In accessory for providing excellent jitter performance, quartz oscillators are you can find at a broad range of sellers.
Quartz Resonator Based Oscillators
Crystal oscillators require a good quartz resonator for each frequency. The crystal oscillator assembly process requires the quartz always be cut, x-rayed, lapped, mounted, and sealed into the final package a. Fabrication of these resonators becomes increasingly difficult at frequencies over 100 MHz when the resonator must be manufactured to very tight tolerances. The complexness of economic downturn process is subject to poor yield at multiple steps tied to the process forcing material restarts and overall production gaps.
In accessory for lead times, reliability is a chief nervous about quartz oscillators. Quartz oscillators are at the mercy of contamination which can affect your center frequency and worn-out of the XO to begin up reliably. If an oscillator fails in the final application, the exact entire system fails simply because the oscillator provides critical timing for the electronics.
MEMS Resonator Based Oscillators
The industry has for ages been searching to obtain technology which allows the replacing quartz oscillators with the most efficient that addresses lead time and reliability concerns while providing performance comparable to quartz oscillators. Over topic several years, micro-electromechanical system (MEMS)-based oscillators have emerged as a likely replacement technology for quartz oscillators. MEMS-based oscillators present an alternative means to quartz by replacing the quartz oscillator with a CMOS-based mechanical resonator.
Si500 Silicon Oscillator
Silicon Lab's Si500 silicon oscillator leverages a standard IC manufacturing flow (Figure 3). The silicon oscillator is fabricated using standard submicron CMOS technology and standard low-cost plastic packaging that doesn't require a hermetic close. The silicon oscillator is factoryprogrammed at test together with specific frequency, signal format, and supply voltage.
Si500 Technology Overview
The heart of the architecture can be a low phase noise, frequency flexible LC oscillator. Using innovative mixed-signal analog circuitry, the oscillator is compensated for frequency variation considering operating temperature range, aging, initial frequency accuracy, supply voltage change, and output loadchange. The silicon oscillator supports a wide frequency range, generating any output clock frequency from 0.9 to 200 Mhz. Selection of the frequency, output type, supply voltage, and output enable (OE) is trapped in non-volatile memory (NVM). At power-on, the Si500 performs a self-calibration using these stored parameters and configures itself for operation.
Temperature stability refers to how much the oscillator frequency varies over mobile phone temperature range of the gps. For the Si500 silicon oscillator, tight temperature stability is achieved through dynamic temperature renumeration. The device has an on-board temperature sensor that, upon detection of a temperature change, dynamically adjusts the frequency of oscillation of the LC oscillator to keep a stable output frequency.
All oscillators experience drift in the frequency over extended periods of time. The effect is called 'aging' and is an important specification on the overall frequency stability overall wedding budget. Aging behavior is dependent on several aging mechanisms just like the design with the resonator, the assembly of the oscillator, ingested level around the resonator, the design of the electronics, along with the operating temperature. To determine an upper bound on aging performance, it is important to control as loads of the mechanisms as possible and to verify conformance through extensive aging studies.
Quartz oscillators require hermetic packaging for your crystal. Package leaks or internal contamination can lead to long term frequency aging, or if severe enough, can even prevent oscillation. Consequently, oscillator manufacturers minimize contamination by using costly, hermetically sealed ceramic or metal packaging and special canning. Done properly, reliable operation can be achieved, but package and assembly costs will be considerably compared to with non-quartz CMOS only devices. As a mechanical device, MEMS resonators are scratching and water damage the same contamination issues and also require hermeticity.
Shock and Vibration
Shock and vibration likewise limit the reliability of quartz-based oscillators. Quartz crystals are mounted above the oscillation electronics using epoxy or metal clips supported on one side only. Attaching the crystal on the whites places the crystal's center of gravity far beyond your the support point allowing the crystal to swing like a diving board when in contact with vibration.
Period jitter is an essential specification for oscillators so it impacts the setup/hold time, noise margin, or bit-error rate of systems which need alignment between clock and data. Period jitter describes how much any period may deviate from top clock period and will be used to determine the setup/hold time margin within be sure you system. Begin to of margin required depends greatly within how many timing violations (i.e., bit-errors) a system can organize. In most designs, no timing violations are allowed over the lifetime of this product, so the amount of margin fairly large. Period jitter is related to phase noise and is usually dominated by phase noise at far offset frequencies up to half in the clock steadiness.
Programmable Output Buffer
Because the Si500 can generate frequencies across a great range (0.9 to 200 MHz), the output buffer design must provide easy connectivity for that many common receiver formats and voltages used in this range. The Si500 employs a programmable output buffer with support for both differential and single-ended formats while easing the design effort by including common external components.
With advances in mixed-signal CMOS technologies, silicon oscillators like the Si500 are now competitive with oscillators that use traditional quartz or MEMS resonators. By reduction of the need for these mechanical resonators, the Si500 offers significantly improved reliability when shock, vibration, and oscillator start up are deemed as. In addition, the Si500's simplified manufacturing flow reduces cost and enables short predictable lead times in comparison to traditional quartz based oscillators.