clock generator Basics

This page covers clock generator basics.It mentions Programmable clock signal generator application note and clock signal generator manufacturers or Vendors.

As we know many digital circuits require a clock signal which is a periodic square wave at a controlled frequency. The circuit which generates clock signal is referred as clock signal generator. There are two types of clock generator namely fixed and programmable or variable. Fixed generator will produce clock signal at fixed frequency. Programmable generator will produce clock signal at varied input and output frequencies.

There are many applications of clock signal generator as mentioned below:
• Wireless base station for LTE, LTE-advanced etc.
• Picocells, femtocells and small cells
• Sampling clocks for ADC and DAC
• 1 Gigabit and 10 Gigabit ethernet
• FPGA and processor clocks
• Line cards used in telephone exchange
• Fiber Channel
• PCI express cards

Programmable clock signal generator Application Note

clock generator

Figure-1 depicts clock generator from Silicon Labs bearing part number Si5380 used as programmable clock signal generator in base station design. As shown it provides sampling clock as input to ADC and DAC. It also provides reference frequency signal as input to synthesizer which is used to provide conversion frequency signal for RF up conversion and down conversion. Refer RF Transceiver basics and design of RF up converter for more information.

This clock generator has very low phase noise and has excellent jitter performance.

Following table mentions features of clock generator from Silicon Labs (part number: Si5380):

Specifications Feature supported
Input frequency range Differential: 10 MHz to 750 MHz
LVCMOS: 10 MHz to 250 MHz
Output fequency range Differential: 480 kHz to 1.47456 GHz
LVCMOS: 480 kHz to 250 MHz
phase noise -159 dBc/Hz
Spurious -103 dBc (Max.)
Serial interface I2C, SPI

clock generator Manufacturers or Vendors

Following are popular clock generator Manufacturers/vendors:
1. Integrated Device Technology, Inc.
2. ON semiconductor
3. Texas Instruments
4. Silicon Labs (
5. Analog Devices

Other Test and Measurement Equipments

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Protocol Analyzer
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Oscilloscope measurements

RF and Wireless Terminologies