Si5351A Breakout Board

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Si5351A Breakout Board

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Product Information

A handy way to use the Si5351A clock generator IC in your RF and microcontroller projects.

The Silicon Labs Si5351A is a fantastic clock generator IC with some features that you won't see anywhere else. It can generate three independent output signals between 8 kHz and 160 MHz (there are some limitations, see Constraints below), using only a simple 25 MHz crystal reference oscillator. Each output can be independently tuned, switched on or off, and have a variable drive level selected. Using an Arduino and a library provided by us, you may control almost every parameter of the IC. The Si5351A is very useful in a variety of applications, such as wide-range VFOs (and can also simultaneously provide a BFO signal), handy signal source, beacon transmitter, or any other project where a stable and tuneable signal is needed.

The Etherkit Si5351A Breakout Board makes it convenient to use the Si5351A with your Arduino or other favorite microcontroller. While the Si5351A is a +3.3 V IC, our board provides a low-dropout voltage regulator and level conversion circuitry so that it can be used with either 3.3 V or 5 V controllers. The three outputs are brougt out to pads which accept SMA female end launch connectors (sold separately) and also to 0.1" headers. You may choose a standard 25 MHz crystal reference oscillator, or an optional high-stability 25 MHz TCXO reference oscillator.

Our boards now include an individually generated calibration report that provides you with the measured frequency of the reference oscillator and the corresponding correction factor in parts-per-billion.
(The calibration is preformed on a spectrum analyzer locked to a GPS disciplined oscillator, and is accurate for hobby usage, but not NIST traceable.)


  • All SMT components assembled, 0.1" headers included separately
  • Fully tested
  • Output frequency range: 8 kHz to 160 MHz (see Constraints below)
  • Number of outputs: 3
  • Output impedance: 50 Ω
  • Output drive levels: 2 mA, 4 mA, 6 mA, 8 mA (into 50 Ω)
  • Power supply: +3.3 V or +5 V
  • Interface: I2C (on a 0.1" header)
  • Output jacks: 0.1" header or optional SMA female end launch
  • PCB material: high quality 1.6 mm double-sided FR4 with soldermask and ENIG coating
  • PCB dimensions: 30 mm x 50 mm
  • RoHS Compliant


Two multisynths cannot share a PLL with when both outputs are < 1.024 MHz or >= 112.5 MHz. This means that you may only have two outputs under those conditions.


20 March 2021 Update: Please note that the calibration factor stated on each Si5351A Breakout Board calibration report has been changed due to some confusion. In previous reports, the calibration factor was written in the sign needed to add or subtract from the nominal 25 MHz ref osc frequency (in other words, if the ref osc was 1000 ppb high, the report would print the correction as "-1000 ppb"). However, in the Etherkit Si5351 Arduino library, the factor you need to use to set the correction has the opposite sign, so in the previous example, you'd need to put in a positive correction, not negative. From this date forward, our calibration reports will use the latter standard, so that you put the number printed on the calibration report as is into the Arduino library correction method.


You will find all of the official documentation at the Etherkit Documentation Wiki. (Note that there is documentation for an older version of this board sold as a kit, but this product has all SMT components assembled.)

Product CodeSI5351ABB

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