An Introduction To Frequency Control

Terminology, Products and Insights You Need To Know When Selecting Crystal Oscillators

Frequency control is the process of maintaining the stability of clocking and timing. Computers today require digital clocks to ensure that processes happen at very specific intervals. Devices like radio frequency transceivers use analog clocking.

Technologically advanced industries, including medtech, automotive, industrial automation and manufacturing, networking and more, all depend on clocking signals from crystal oscillator circuits for the synchronization, organization and orchestration they provide.

As you begin the design process for applications that require timing solutions, use this guide to inform your conversations with ECS Inc., the leading manufacturer of frequency control products.

Need-To-Know Timing Acronyms

These acronyms will help you understand a clock signal’s frequency when it is generated by a crystal oscillator circuit.

• Hz: Hertz; 1 cycle per second.
• kHz: Kilohertz; 1,000 Hz per second.
• MHz: Megahertz; 1,000,000 Hz per second.
• GHz: Gigahertz; 1,000 MHz.
• mS: Millisecond; 1/1,000th of a second.
• µS: Microsecond; 1/1,000,000th of a second.
• nS: Nanosecond; 1/1,000th of a microsecond
• pS: Picosecond; 1/1,000th of a nanosecond.
• fs: Femtosecond; 1/1,000th of a picosecond.

Common Frequencies In Electronics

Frequency is an essential part of our lives in a connected, technologically advanced world. These frequencies are used in the devices, appliances and equipment that populate our lives at home and the workplace.

• 50 Hz: The frequency of A/C power in the United Kingdom.
• 60 Hz: The frequency of A/C power in the United States.
• 32.768 kHz: The frequency of real time clocks (RTC).
• 13 MHz / 26 MHz: The frequencies of GSM and LTE cellphone clocks.
• 13.56 MHz: RFID (radio frequency identification) and NFC (near field communications) frequencies.
• 900 MHz: A common mobile GSM (global system for mobile communications) frequency.
• 1575.42 MHz: A common GPS frequency.
• 2450 MHz / 2.45 GHz to 5000 MHz / 5 GHz: Common Wi-Fi frequencies.
• RF: The radio frequency bandwidth is typically 3 kHz to 300 GHz.

Common Terms In Frequency Control

When determining how to use a frequency signal from a crystal oscillator circuit, these terms will help you understand how high-quality clock manufacturers refer to the products they design.

• Quartz: A single crystal of silicon dioxide (SIO2), which is cut using an etching or grinding process to create a specific frequency.
• Nominal frequency: This is the specified center frequency, also known as the standard operating frequency for a given electronic device.
• Fundamental mode: The primary frequency of crystal cut.
• Overtone (3rd, 5th, 7th, etc.): These are the integral multiples of the fundamental frequency.
• AT-Cut: The most common angle cut for quartz crystals.
• Quartz blank: A finished crystal which is mounted in a holder.
• Crystal electrodes: Plated areas on both sides of a quartz crystal blank.
• TH crystal: A through-hole crystal, which has leads that are threaded through holes drilled in the printed circuit board.
• SMD crystal: A surface mounted crystal is installed directly onto the circuit board.
• ESR: Equivalent series resistance refers to the amount of loss that capacitors and inductors experience during circuit operation.
• CL: Load capacitance refers to the amount of external energy that is stored when a capacitor is in operation.

Common Oscillator Terminology

The following is a list of the most commonly used oscillators, which are available from ECS Inc. for the projects you design.

• 32.768 kHz: This quartz-generated frequency is common for watches or devices with time-keeping functionality.
• XO: The abbreviation for a crystal clock oscillator.
• VCXO: A voltage controlled crystal oscillator applies voltage to move an oscillator’s frequency to match that of the frequency being transmitted or received.
• TCXO: Temperature compensated crystal oscillators adjust the frequency to guard against the effects of temperature on the signal.
• VC-TCXO: A voltage controlled temperature compensated crystal oscillator allows for frequency adjustment, like a VCXO, alongside frequency stabilization due to adverse temperatures, like a TCXO.
• OCXO: An oven controlled crystal oscillator has an internal heater and temperature control circuit to maintain the crystal inside at its “turn-point.” OCXOs will offer considerably better stability, jitter and phase noise.
• MultiVoltTM: MultiVoltTM oscillators are quartz based and are the preferred oscillator configuration. MV oscillators are available at 32.768 kHz, as MHz oscillators and as TCXOs. There are low jitter, tight tolerance, low current and available as AEC-Q200 qualified products. Overall, MultiVoltTM oscillators offer better performance at a lower cost than comparative MEMS devices.
• Programmable: Digitally programmable oscillators allow a user to adjust the oscillator’s frequency through an interface.
• AEC-Q200: This code is the global standard for automotive-grade passive components, such as crystal oscillators.

Common Oscillator Output Terms

Engineers in the design community who depend on timing solutions for their applications use these terms to describe the frequency output of their crystal oscillator circuits.

• TTL: Transistor-transistor logic is an ASIC built with bi-polar junctions and resistors that use a 5V supply.
• LVCMOS / CMOS: A low voltage complementary metal oxide semiconductor is a low voltage class of CMOS technology found in integrated circuits. They are often 3.3V, but JEDEC (Joint Electron Device Engineering Council) standards allow a voltage as low as 1.1V.
• LVDS: Low voltage differential signaling can operate at a low power point and can run at very high speeds. These often have a 2.5V supply and can be used in applications requiring >100 MHz.
• LVPECL: Low voltage emitted couple logic are differential signaling systems, primarily used in high speed and clock distribution circuits.
• HCSL: High speed current steering logic is a differential logic output producing 0V and 0.725V supply swings. It is used for low jitter and low electromagnetic interference applications.
• Clipped sine wave: A sinusoidal waveform where the upper and lower peaks have been manipulated, so it will not reach its high or low. This results in a square wave output without sacrificing any of the desired phase noise performance.

• Sine wave output: A sine wave is an alternating current (AC) analog signal in the shape of a sine wave. These are essential in many electronic devices, including computers, cell phones, radar and radio and television receivers and transmitters. Sine wave oscillators are useful because they can generate accurate, repeatable frequencies.

Insights On Today’s Crystal Package Sizes

The form factor of today’s crystal oscillators is a product of the ways electronics technology has evolved in recent years to provide users with the most efficient applications.

Crystal packages are getting smaller every day. Currently, ECS Inc. carries both 1.2 x 1.0 mm and 1.6 x 1.2 mm package sizes. Globally, the most common crystal package size is 3.2 x 2.5 mm. In fact, 32.768 kHz watch crystals are getting smaller, as well, with the most common sizes being 3.2 x 1.5 mm or 1.2 x 1.0 mm.

Although sales of smaller package sizes are growing each year, demand to reduce bill of materials costs is often paramount. So, HC-49 SM packages like the CSM-7X (5PX) are still global best-sellers.

Oscillators are also trending smaller than ever before. ECS Inc. is seeing an uptick in sales on parts like the ECS-1612MV, the smallest available MHz oscillator at 1.6 x 1.2 mm. Over the last five years, the most popular oscillator packages have been 3.2 x 2.5 mm and the 2.5 x 2.0 mm.

ECS Inc. TCXOs are common in sizes ranging from 2.0 x 1.6 mm to 7.0 x 5.0 mm packages that are necessary for a variety of applications including GPS. Both CMOS and clipped sine wave outputs are available, depending on use in either an analog or digital application. MultiVolt™ TCXOs are quickly improving to a point where they have replaced traditional TCXOs.

Begin a Partnership For Your Frequency Control Solutions

Perhaps the most important information you can glean about frequency control is how to develop a relationship with a manufacturer that produces high-quality, high-performing, timing solutions.

For over 40 years, ECS Inc. has provided engineers with the timing components and engineering support they require for critical applications in a wide range of industries. ECS Inc. continues to meet engineers’ needs, as new technologies emerge, including Internet of Things (IoT), Artificial Intelligence (AI) and more advanced data networking and communications.

Visit the ECS Inc. portfolio of products today to discover their robust line of clocking solutions.