Si5351A/B/C

5.4. Replacing Crystals, Crystal Oscillators, and VCXOs

The Si5351B combines free-running clock generation and a VCXO in a single package for cost sensitive video applications. An example is shown in Figure 14.

 

 

 

 

 

Free-running

 

 

 

 

 

 

Clocks

 

XA

 

 

Multi

CLK0

125 MHz

Ethernet

 

 

 

 

PHY

 

 

 

Synth

 

 

 

27 MHz

OSC

PLL

0

CLK1

 

 

Multi

 

 

XB

 

 

48 MHz

USB

 

 

 

 

 

 

Synth

 

 

Controller

 

 

 

1

 

 

 

 

 

Multi

CLK2

28.322 MHz

 

 

 

 

Synth

 

 

 

 

 

 

 

HDMI

 

 

 

2

 

 

 

 

 

 

 

 

Port

VC

 

 

Multi

CLK3

74.25 MHz

 

 

 

Synth

 

 

 

 

 

VCXO

3

CLK4

 

 

 

 

Multi

 

 

 

 

 

74.25/1.001 MHz

Video/Audio

 

 

 

Synth

 

 

Processor

 

 

 

4

 

 

 

 

 

CLK5

 

 

 

 

 

Multi

24.576 MHz

 

 

 

 

Synth

 

 

 

 

Si5351B

 

5

 

Synchronous

 

 

 

 

 

 

 

 

 

 

 

Clocks

 

Note: FBW = 10 kHz

 

 

 

 

 

 

Figure 14. Using the Si5351B to Replace Crystals, Crystal Oscillators, VCXOs, and PLLs

5.5. Replacing Crystals, Crystal Oscillators, and PLLs

The Si5350C generates synchronous clocks for applications that require a fully integrated PLL instead of a VCXO. Because of its dual PLL architecture, the Si5351C is capable of generating both synchronous and free-running clocks. An example is shown in Figure 15.

25 MHz

54 MHz

Free-running

Clocks

XA

 

Multi

CLK0

125 MHz

Ethernet

 

 

 

PHY

 

 

Synth

 

 

OSC

PLL

0

CLK1

 

 

Multi

 

 

XB

 

48 MHz

USB

 

 

 

 

Synth

 

 

Controller

 

 

1

 

 

 

 

Multi

CLK2

28.322 MHz

 

 

 

Synth

 

 

 

 

 

 

HDMI

 

 

2

 

 

 

 

 

 

 

Port

 

 

Multi

CLK3

74.25 MHz

 

CLKIN

 

Synth

 

 

 

 

PLL

3

CLK4

 

 

 

Multi

 

 

 

 

74.25/1.001 MHz

Video/Audio

 

 

Synth

 

 

Processor

 

 

4

 

 

 

 

CLK5

 

 

 

 

Multi

24.576 MHz

 

 

 

Synth

 

 

 

Si5351C

 

5

 

 

 

 

 

 

 

 

 

 

 

 

Synchronous

 

 

 

 

 

Clocks

 

Figure 15. Using the Si5351C to Replace Crystals, Crystal Oscillators, and PLLs

Preliminary Rev. 0.95

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Silicon Laboratories SI5351A/B/C specifications Replacing Crystals, Crystal Oscillators, and VCXOs, Si5351B, Si5351C

SI5351A/B/C specifications

Silicon Laboratories SI5351A/B/C is a versatile, low-power clock generator and frequency synthesizer that has gained widespread popularity in various applications, including telecommunications, consumer electronics, and industrial control systems. These devices are primarily designed to provide precise clock frequency generation with low phase noise and jitter, making them ideal for high-performance applications.

One of the standout features of the SI5351 is its ability to generate multiple output frequencies simultaneously. Capable of producing up to three independent programmable outputs, the SI5351A/B/C can generate frequencies ranging from 8 kHz to 160 MHz. With its integrated phase-locked loop (PLL) technology, it achieves excellent frequency stability and accuracy, simplifying the design of frequency-dependent systems.

The device operates under a supply voltage range of 1.8V to 3.6V, allowing it to be used in battery-powered applications without excessive power consumption. The SI5351’s low current draw, typically as low as 25 mA, is especially beneficial in portable devices, extending battery life and enhancing overall efficiency. Furthermore, it features a programmable output driver, which can be set to various drive strengths, ensuring compatibility with a wide array of load requirements.

Configuration and control of the SI5351 are user-friendly, implemented via an I2C interface. This allows for straightforward integration into microcontroller-based designs. Moreover, the device includes an on-chip memory that stores settings, which streamlines the reconfiguration process when power cycling, minimizing setup time for developers.

Another significant advantage of the SI5351A/B/C is its output jitter performance, which is typically below 1 ps, resulting in clean output signals essential for high-speed data communications and precise timing applications. The SI5351’s integration of multiple synthesizer stages contributes to its impressive phase noise characteristics, making it suitable for demanding RF applications.

Additionally, the SI5351 devices offer programmable frequency stepping, allowing users to define custom frequency increments, which is particularly useful in applications requiring precise tuning or modulation. This flexibility, combined with its compact size and simple interface, makes the SI5351A/B/C an ideal choice for engineers seeking a reliable, cost-effective solution for generating clock signals in a myriad of electronic systems.

In summary, Silicon Laboratories SI5351A/B/C provides a robust, low-power solution for high-precision clock generation, characterized by its programmable outputs, low jitter, easy configurability, and broad frequency range, making it an excellent choice for both commercial and industrial applications across various sectors.