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Introduction to Frequency Control Products

Introduction to Frequency Control Products

Written by David Meaney, Vice President of Global Technical Sales and Marketing at ECS Inc. International

Frequency control is the process of maintaining the stability of clocking and timing in digital devices. All digital circuits today require clocks to ensure that processes happen at very specific intervals.

In the 1970’s, the digital watch was introduced. The design used kHz watch crystals to keep the timing, which is a process we still use today. Real-Time Clocks (RTC) are used to timing in most processors and are used in registers as counters. Oscillators provide RF signals and TCXOs are used in two-way communication devices to provide clear communication. 

Crystals 

Crystal packages are getting smaller every day. Currently, ECS Inc. International 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. 32.768 kHz watch crystals are getting smaller as well with the most common size being the 3.2 x 1.5 mm or the 1.2 x 1.0 mm. While sales of smaller package sizes are growing each year, demand to reduce BOM cost is often paramount. So, HC-49 SM packages like our CSM-7X (5PX) are still global best-sellers. Crystals are used most often in processors. They require matching caps on the PCB to make the oscillator loop.

Oscillators 

Oscillators are also trending smaller than ever before. We are seeing an uptick in sales on parts like our ECS-1612MV, our smallest MHz oscillator at 1.6 x 1.2 mm. Over the last 5 years, our most popular oscillator packages have been 3.2 x 2.5 mm and the 2.5 x 2.0 mm. Our MultiVoltTM Oscillators are quartz based and are the preferrerd 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 AEC-Q200 options available. Overall, MV oscillators offer better performance at a lower cost than comparative MEMS devices.

TCXOs + OCXOs

TCXOs are common in sizes ranging from 2.0 x 1.6 mm up to 7.0 x 5.0 mm packages that are necessary for a variety of applications including GPS. We offer both CMOS and Clipped Sine Wave outputs depending on use in either an analog or digital application. MultiVolt™ TCXOs are quickly improving to a point where they can be considered to replace traditional TCXOs. OCXOs are oscillators that have an internal heater and temperature control circuit to maintain the crystal inside at it’s “turn-point”. OCXOs will offer considerably better stability, jitter, and phase noise. Design and manufacturing of OCXOs are more expensive than other oscillators.  

Timing Acronyms

Hz - Hertz; 1 cycle per second
kHz - Kilo Hertz; 1,000 Hz per second
MHz - Mega Hertz; 1,000,000 Hz per second
GHz - Giga Hertz; 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

50 Hz - Frequency of A/C power in the UK
60 Hz - Frequency of A/C power in the U.S.
32.768 kHz - Frequency of Real Time Clocks (RTC)
13 MHz / 26 MHz - Frequencies of GSM and LTE cell phone clocks
13.56 MHz - RFID and NFC frequencies
900 MHz - Common mobile GSM frequency
1575.42 MHz - Common GPS frequency
2450 MHz / 2.45 GHz to 5000 MHz / 5 GHz - Common Wi-Fi Frequency
RF - Radio frequency bandwidth typically 3 kHz to 300 GHz

Common Terms in Frequency Control

Quartz - A single crystal of Silicon Diocide (SIO2 )
Nominal Frequency - Specified center frequency
Fundamental Mode - Primary frequency of crystal cut
Overtone (3rd, 5th, 7th, etc.) - Integral multiples of the fundamental frequency
AT-Cut - Most common angle cut of crystals
Quartz Blank - Finished crystal which is mounted in holder
Crystal Electrodes - Plated areas on both sides of the blank
TH Crystal - Thru Hole Crystal
SMD Crystal - Surface Mount Crystal
ESR - Equivalent Series Resistance
CL - Load Capacitance

Common Oscillator Basics Terms

32.768 kHz - Common watch frequency
XO - Crystal Clock Oscillator
VCXO - Voltage Controlled Crystal Oscillator
TCXO - Temperature Compensated Crystal Oscillator
VC-TCXO - Voltage Controlled Temperature Compensated Crystal Oscillator
OCXO - Oven Controlled Crystal Oscillator
MultiVolt™ - MultiVoltTM Oscillators including 32 kHz, XOs, and TCXOs
Programmable - Digitally programmable oscilliators
AEC-Q200 - Qualification of automotive grade oscillators

Common Oscillator Output Terms

TTL - Transistor-Transistor Logic
An ASIS built with bi-polar junctions and resistors that use a 5V supply

LVCMOS / CMOS - Low Voltage Complementary Metal Oxide Semiconductor
A low voltage class of CMOS technology found in integrated circuits; often 3.3V but JEDEC standards allow down to 1.1V

LVDS - Low Voltage Differential Signaling
Can operate at a low power point and can run at very high speeds; often 2.5V supply and can be used in applications requiring <100 MHz

LVPECL - Low Voltage Emitted Couple Logic
Differential signaling systems and are primarily used in high speed and clock distribution circuits

HCSL - High Speed Current Steering Logic
Differential logic output producing 0V and 0.725V supply swings; Used for low jitter and low EMI applications

Cipped Sine Wave
Sinusoidal wave form where the upper and lower peaks have been clipped off - beyond the capability of the amplifer and not needed. This results in a distorted square wave form

wavelength 2

 

Use the following links to our library of technical resources:

Technical Guides

Video Learning

2021 ECS Catalog

Reference Designs

About ECS

Founded in 1980, ECS Inc. International has grown to become one of the most recognized and experienced manufacturers of frequency control management products in the world.
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