Programmable Clock Oscillators Provide the Right Reference Clock, Every Time

A reference clock oscillator in electronics has long been the domain of fixed-frequency devices. These devices have historically consisted of a quartz crystal, which has been cut and manufactured to operate at a precise, fixed frequency, married to an analog oscillator circuit, which operates at the same fixed frequency and a fixed voltage. The process of manufacturing these fixed-frequency oscillators has been optimized over time, and results in accurate clocking devices that are very inflexible in offering features.

With recent advances in semiconductor-based MEMS technology and analog circuits, these fixed frequency clock oscillators are rapidly being replaced by a programmable clock oscillator. Programmable clock oscillators use a fixed frequency MEMS resonator, married with a programmable analog circuit which can offer a host of features that are not available from fixed-frequency oscillators, such as

1. Any frequency within the operating range, achievable by using a highly accurate Phase Locked Loop (PLL) which can multiply the MEMS resonator frequency up to any desired frequency of operation. The output frequency is accurate up to 6 decimal places of accuracy (1 Hz). This is particularly useful in applications where non-standard frequencies are desired to improve performance and reduce error rates.

2. Ability to operate at any voltage between 2.5V and 3.3V, as well as 1.8V, which are the most common input-output voltages used in electronics.

3. Programmable drive strength control using SoftEdge technology, which allows the user to accurately match the output impedance of the clock oscillator with the trace impedance of the board, and thus reduces reflections. Higher drive strength can also be used for driving multiple loads, while lower drive strength can be used for reducing electromagnetic interference (EMI).

4. Ability to configure the output control pin into Output Enable or Standby. In the case of more-featured oscillators such as Voltage Controlled Oscillators (VCXOs) and Voltage-Controlled, Temperature Compensated Oscillators (VC TCXOs), the programmability of the device also allows easy configuration of the pull range.

With such a host of features available from programmable clock oscillators, it is no surprise that the devices are rapidly gaining in popularity and have already replaced a significant number of fixed frequency reference oscillators.

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Crystal Oscillator

Top Five Reasons to Replace your Quartz Oscillator

A quartz oscillator (also known as a crystal oscillator) has been the reference clock of choice in the electronics industry for many decades. Recently, this legacy device has been under attack by a host of clock devices that use a newer, more advanced technology - Silicon MEMS. Here are the Top Five reasons why you should replace yourquartz oscillatorwith a Silicon MEMS device.

1. Higher Performance:
Silicon MEMS oscillators offer higher performance across a wide spectrum of parameters. A quartz oscillator has been optimized for specific parameters - such as phase noise at a particular frequency and operating voltage and does extremely well. Silicon MEMS oscillators not only perform extremely well on these specific parameters - but they also offer high performance other parameters, such as:

a.Stable and reliable startup over temperature (which is an inherent problem in quartz oscillators due to the activity dips of crystals)

b.Full frequency range available at 1.8V, which is not commonly available from quartz devices.

c.Oscillator stability as good as 10 PPM, which is not commonly available from quartz devices (MEMS TCXOs offer stability as good as 0.1 PPM)

2. More Features:
Silicon MEMS oscillators offer many more features than a quartz oscillator. Some of these features are listed below.

a.Any frequency, up to 6 decimal places of accuracy. This capability is useful for generating higher performance or lower error rates from systems.

b.Drive strength control for better impedance matching, ability to drive multiple loads, or reduced EMI.

c.Thinner packages for thinner electronics.

d.Operation at custom voltages between 2.5V and 3.3V.

3. Better availability:
Production lead times of Silicon MEMS oscillators are 3-5 weeks, while that of a quartz oscillator is 6 - 16 weeks. This reduction of lead time ensures that Silicon MEMS oscillators can reduce inventory and cost of ownership.

4. Better robustness and reliability:
Silicon MEMS oscillators are based on Silicon, and use no quartz. They offer 10 times more robustness (ability to withstand shock and vibration) than quartz oscillators, as well as ten times better reliability.

5. Better cost trajectory:
Silicon MEMS oscillators have a better cost trajectory than quartz oscillators because they are based on Silicon and leverage the semiconductor industry infrastructure.

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Crystal Oscillator

The Clock Oscillator: The Shift from Quartz to MEMS

The technological era has given birth to numerous electronic gadgets. One of the most popular electronic devices ever invented is the clock. Eventually technology enabled the use of electo-mechanical  resonators to generate a reliable, accurate frequency for all clocks.  This became known as the modern reference clock.  With its stable, repeatable waveform, the reference clock is the heartbeat of an electronic product.  In essence, a clock is the most important component for operation of an electronic device as it controls timing. Depending on the application requirements, various timing components such as resonators, oscillators and clock generators can be used as reference sources. However, most electronic systems such as hard drives, cameras, video cards and computer systems use several clock oscillators to provide accurate timing necessary for the proper operation of the system.
 

Based on quartz oscillator technology, these clock oscillators were made by using precision manufacturing techniques.  Consisting of three components; a resonator, an analog excitation circuit plus a standard logic output driver, and a package, the oscillator’s main performance parameters include - frequency range and resolution, stability and tolerance, jitter, power consumption, operating supply voltage, and temperature range. However, the advent of technological innovation has paved way for the wide spread adoption of the Micro-Electro-Mechanical Systems (MEMS) resonator instead of quartz in the electronics industry.  This has given rise to the design and development of a programmable clock oscillator, which can customize the oscillator frequency and has been adopted in devices such as Smart Phones, Tablets, Digital Cameras and gaming systems.
 

The past few years have seen the quartz crystal oscillators being replaced by the MEMS Oscillators in various electronic applications. With a number of benefits such as better features, higher performance, faster availability, higher robustness, lower cost and increased reliability, the MEMS Oscillators score higher than its counterpart in the adoption processes. These features have given these oscillators a place in Telecom infrastructure routers and optical networking systems, which uses the TCXOs (Temperature Compensated Oscillators) for their high performance applications. Further, VCXOs or Voltage Controlled Oscillators provide a level of pullability and fine-tuning that is required for synchronization of clock signals, in wireless applications, cell phones and base-stations. These are also used in Storage Area Networks and RAID systems based on SATA, SAS and Fibre Channel protocols.
 

The MEMS based clock oscillators can be programmed for any frequency levels with performance optimization and flexibility.  MEMS oscillators achieved unparalleled stability and low jitter performance.  XOs achieve +/-10 PPM stability over the -40C to +85C temperature range, and their TCXOs achieve 0.500 PPM stability over the same operating temperature range.  Both devices also feature ultra-low jitter as low as 0.5psRMS. Further, these can be programmed for any supply voltage as low as 1.8V. Most importantly programmable MEMS oscillators simplify the supply chain with shorter lead times and fewer dedicated parts at discrete frequencies. The superior frequency stability as low as 10 PPM (XO) improves  system timing margin and reliability and leads to longer life of the electronic systems.

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Quartz Oscillator 
TCXO Oscillator