ADF4351 PLL Synthesizer Module

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ADF4351 PLL Synthesizer Module (Built & Tested PCB Module)

  • Best Phase-Noise ADF4351 Module
  • 35MHZ to 4400 MHZ  Miniature size
  • ​Make a VFO, Clock Gen etc. fast
  • Now with footprint for a Reference TCXO just under the external REF SMA connector


Based on the Analog Devices ADF4351 chip, this small module is a complete PLL Synthesizer working from 35 MHZ to 4..4 GHZ.

The ADF4351 allows implementation of fractional-N or integer-N phase-locked loop (PLL) frequency synthesizers when used with an external loop filter and external reference frequency if the on-board 10 MHZ is not used. The ADF4351 has an integrated voltage controlled oscillator (VCO) with a fundamental output frequency ranging from 2200 MHz to 4400 MHz. In addition, divide-by-1/-2/-4/-8/-16/-32/-64 circuits allow the user to generate RF output frequencies as low as 35 MHz. Control of all on-chip registers is through a simple 3-wire interface. The ADF4351 module draws under 60 mA - 100 at 3.3 VDC, depending on the output power set and if the frequency dividers are being used. 

The PCB dimensions are only 25 x 38 mm and it requires an external frequency reference that can be applied to J5 SMA female connector if the on-board 10 MHZ TCXO is not used. In this case remove L7 which powers the TCXO with 3.3VDC.

A small Arduino or any other MCU can be used to control the ADF4351 module, and the "cheat sheet" provided at the end of this page is really a great help. Considering its small size and the simplicity this module provides, a user can quickly produce an RF signal, phase-locked to his reference and also to control the output power, this module can find many applications like a VFO, fixed frequency oscillator, ADC or DAC clock etc. Interesting features are the capability to adjust phase, to set low spur or low noise and of course the capability to select Integer-N for lowest phase noise. Adding a large capacitor on the supply rails reduces phase noise more.


The PCB Module includes a  high-quality ENIG FR4 PCB (25 x 38 mm) that comes with all SMD components factory pre-soldered. RF capacitors are used for all the circuits.  

Three SMA female connectors (long shaft) with nuts and washers are also supplied, soldered. 

For code examples also see here

and here

Another project description is here: A great work of Dave Fannin, KK6DF

A special contoller board which can be plugged in right on top of an ADF4351 PCB module can be separately supplied. This board has its own controller which can program the ADF4351 registeres upon power up or PTT change to store 1 or two frequencies. This controller has an on-board 10 MHZ reference oscillator supplied with 2 options, one with 2.5 ppm stability and another with 0.28 ppm stability. Please check the products shown below for more details.