Si5351A Clock Generator Module

8KHZ to more than 150 MHZ

with 3 independent outputs

With Ultra-Low-Noise Voltage Regulator and 10 ppm 27 MHZ crystal

Based on the Silicon Labs Si5351A chip, this small module is a complete clock generator working from below 8 KHZ to more than 150 MHZ.

The Si5351A chip uses an external precision crystal to make a precision clock signal that uses it to drive multiple PLL's and clock dividers using I2C instructions. By setting up the PLL and dividers one can create precise and arbitrary frequencies. There are three independent outputs, and each one can have a different frequency. Outputs are 3Vpp and it draws under 35 mA at 3.3 VDC. The PCB module also has a 3.3V ultra low-noise voltage regulator.

The external crystal is of special order to match the Silicon Labs AN-551 application note's requirements.

The I2C interface can be terminated to 10K resistors both at 3.3V or at 5V using the jumper J4. If your I2C bus is already terminated you can remove this jumper.

Also two MOSFET switches allow automatic interfacing to both 3.3V or 5V MCU systems.

The 5-pin connector J5 gets +5V DC for power, ground and the SDA and SCL signals of the I2C bus.

The PCB dimensions are only 32.5 x 31 mm and those 4 mounting holes aids for crystal's mechanical stability if the pcb is to be used in portable equipment..

Possible uses of this module is a general purpose clock generator at any frequency needed, eliminating the need of a special or hard-to-find crystal oscillator, a VFO for a QRP radio, a VFO/BFO for dual conversion radios, including the ability to shifting the VFO and BFO frequencies at the same time in order to offer an "IF-Shift" function, a VFO for SDR radios, a system-internal BITE oscillator, etc.

The frequency stability and its spectral purity is more or less similar or better to the older Si570 types, well acceptable for operation in ham radio equipment, well, not enough for very narrow modes like WSPR etc.

Generally it is a great performer considering its low price and its quick and simple implementation.

The Module includes a  high-quality ENIG FR4 PCB (32.5 x 31 mm) that comes with all SMD components factory pre-soldered. 

RF capacitors are used for all the circuits.  

Three SMA female connectors with nuts and washers are also supplied, unsoldered. 

Konstantinos, SV1ONW Article for a Si5351A-based VFO project in English - First published in Greek in SV-QRP magazine (Dec 2015 issue).