SI5335 Datasheet, PDF (36/47 Pages) Silicon Laboratories – WEB-CUSTOMIZABLE, ANY-FREQUENCY, ANY-OUTPUT QUAD CLOCK GENERATOR/BUFFER

Si5335
9. Applications of the Si5335
Because of its flexible architecture, the Si5335 can be configured to serve several functions in the timing path. The
following sections describe some common applications.
9.1. Free-Running Clock Generator
Using the internal oscillator (Osc) and an inexpensive external crystal (XTAL), the Si5335 can be configured as a
free-running clock generator for replacing high-end and long-lead-time crystal oscillators found on many printed
circuit boards (PCBs). Replacing several crystal oscillators with a single IC solution helps consolidate the bill of
materials (BOM), reduces the number of suppliers, and reduces the number of long-lead-time components on the
PCB. In addition, since crystal oscillators tend to be the least reliable aspect of many systems, the overall failure-in-
time (FIT) rate improves with the elimination of each oscillator.
Up to four independent clock frequencies can be generated at any rate within its supported frequency range and
with any of supported output types. Figure 25 shows the Si5335 configured as a free-running clock generator.
XTAL
Osc ^ref PLL
MS0
F0
MS1
F₁
MS2
F₂
MS3
F₃
Si5335
Figure 25. Si5335 as a Free-Running Clock Generator
9.2. Synchronous Frequency Translation
In other cases, it is useful to generate an output frequency that is synchronous (or phase-locked) to another clock
frequency. The Si5335 is the ideal choice for generating up to four clocks with different frequencies with a fixed
phase relationship to an input reference. Because of its highly precise frequency synthesis, the Si5335 can
generate all four output frequencies with 0 ppm error to the input reference. The Si5335 is an ideal choice for
applications that have traditionally required multiple stages of frequency synthesis to achieve complex frequency
translations. Examples are in broadcast video (e.g., 148.5 MHz to 148.3516483 MHz), WAN/LAN applications (e.g.
155.52 MHz to 156.25 MHz), and Forward Error Correction (FEC) applications (e.g., 156.25 MHz to
161.1328125 MHz). Figure 26 shows the Si5335 configured as a synchronous clock generator. Frequencies may
be entered into the ClockBuilder Web utility with up to seven decimal points to ensure that the exact frequencies
can be achieved.
Si5335
MS0
F₀
CLKIN
MS1
F₁
PLL
MS2
F₂
MS3
F₃
Figure 26. Si5335 as a Synchronous Clock Generator or Frequency Translator
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Rev. 1.4