Update: You can now order Si5351A Breakout Board partial kits from our store at etherkit.com!

What's This All About?

Hello, my name is Jason Milldrum, and I'm the owner of Etherkit, a small business specializing in open source hardware for radio amateurs. I hold the amateur radio licence NT7S and I also blog at Ripples in the Ether. You can read more about me on my profile page.

Over approximately the last year, I (along with some other folks) have been working on characterizing the Silicon Labs Si5351A clock generator IC for use in amateur radio and other RF applications. I have posted the results of those experiments on my blog. I've also written a library for driving the Si5351A with an Arduino, which has already been put to use by other people in radio projects.

The Si5351A is quite a capable IC at a very modest price. It is a PLL clock generator with three independent outputs which can each generate a separate signal from 8 kHz to 160 MHz. A 25 or 27 MHz reference oscillator is used for the two internal PLLs (the Etherkit breakout board uses a 25 MHz reference oscillator), which allows the user to choose the amount of frequency stability and accuracy required. 

In the past few months, I have also been developing a Si5351A breakout board, which allows the IC to be easily used with a microcontroller, Arduino, or other development board that has I2C capability. This breakout board gives access to the three Si5351A clock outputs via either SMA female connector or 0.1 inch header. The board is designed to accommodate either a standard 25 MHz crystal reference oscillator or a more stable 25 MHz TCXO, at the choice of the builder. Also included is a 3.3 volt LDO voltage regulator and I2C level shifting so that the Si5351A can be interfaced to either 3.3 volt or 5 volt systems.

All of these features, along with the firmware library, make it a snap to put the Si5351A to use in your next project, according to your needs. The three independent outputs make it a perfect fit to use as a VFO and BFO in a superheterodyne receiver or transceiver. The fine tuning steps (1 Hz with the current Arduino library) and large frequency range make it an excellent choice for projects such as an antenna analzyer, signal generator, or clock generator. The optional TCXO makes the Si5351A Breakout Board especially useful in applications where high-stability is needed, such as in a WSPR or QRSS transmitter.

This is a fully open source hardware project. All design files will be released under a Creative Commons CC-BY-SA licence on GitHub (in KiCad format). Although it is currently not complete, you can view the GitHub repository for the project here. A PDF of the Rev B schematic is available there, although campaign backers will receive a Rev C PCB, which removes the output transformers and has a few minor fixes, but is otherwise similar. Also, the image used above is the Rev B PCB and shows the optional SMA end launch connectors. The Rev C PCB will be similar in design, excluding the output transformers. The PCB size is expected to be approximately 30 x 50 mm.

The Campaign Details

Etherkit is considering funding our upcoming CC1 CW QRP transceiver via a crowdfunding campaign, so we wanted to get some experience with a smaller project first. We feel that this Si5351A Breakout Board is an ideal first step for us, as we have a modest funding goal of $500 to have our campaign move forward. If we meet or exceed our $500 goal, all campaign perks (mostly product) will be fulfilled. If the goal is not met, then your contribution will be fully refunded to you.

Funds raised here will help us to bring the Si5351A Breakout Board to the Etherkit Web Store as a regular product that we carry. A successful campaign will also help us to gauge which of the product options that are most wanted, so that we know which ones to regularly keep in stock.

Campaign Perks

This is a hardware launch, and the majority of campaign perks will be deliveries of actual hardware. The hardware perks will be four different varieties of the Si5351A Breakout board, each of them a kit that is assembled by the end user (it requires the ability to solder TSSOP, SOT, and 0805 passive SMT components):