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CJMCU-5351 Si5351A Clock Generator Module — I2C, 8kHz–160MHz for Arduino & SDR
CJMCU-5351 Si5351A Clock Generator Module I2C, 8kHz–160MHz for Arduino & SDR
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CJMCU-5351 Si5351A Clock Generator Module — I2C, 8kHz–160MHz
The CJMCU-5351 breakout module is built around Silicon Labs’ Si5351A programmable any-frequency clock generator IC. It provides three independent, phase-coherent clock outputs from 8kHz to 160MHz, all configurable via I2C from an Arduino, Raspberry Pi, or any microcontroller. With a 25MHz TCXO reference and fractional-N PLL synthesis, it generates precise, stable frequencies for software-defined radio (SDR) VFOs, signal generators, frequency counters, and clock distribution applications.
Key Specifications
| Parameter | Value |
|---|---|
| IC | Silicon Labs Si5351A |
| Output Channels | 3 independent clock outputs (CLK0, CLK1, CLK2) |
| Frequency Range | 8kHz – 160MHz per output |
| Frequency Resolution | Sub-Hz (fractional-N PLL) |
| Interface | I2C (address 0x60) |
| Supply Voltage | 3.3V / 5V compatible (onboard regulator) |
| Output Level | 3.3V CMOS square wave |
| Phase Coherence | Yes — outputs share PLL reference |
| Reference Crystal | 25MHz (onboard) |
| Origin | CN |
Why Choose the Si5351A?
- 3 independent outputs — Generate three different frequencies simultaneously; ideal for IQ signal generation (90° phase offset) in SDR applications
- Sub-Hz resolution — Fractional-N PLL synthesis allows extremely fine frequency steps across the full 8kHz–160MHz range
- I2C control — Simple 2-wire interface; no SPI bus conflicts; works with any I2C-capable microcontroller
- Wide library support — Adafruit Si5351 Arduino library provides easy frequency setting, phase control, and output enable/disable
- Phase-coherent outputs — All outputs derived from the same PLL reference; enables quadrature (I/Q) signal generation for direct-conversion SDR receivers
Typical Applications
- Software-defined radio (SDR) VFO and local oscillator
- Arduino / Raspberry Pi signal generator (audio to HF range)
- Frequency counter reference clock
- QRP amateur radio transceiver VFO
- Clock distribution for multiple MCU or FPGA modules
- Quadrature (I/Q) signal source for direct-conversion receivers
Frequently Asked Questions
Q: Can the Si5351A output above 160MHz?
The Si5351A is specified to 160MHz. Some units may operate up to 200MHz with reduced output amplitude, but this is outside the guaranteed specification. For frequencies above 160MHz, consider the Si5351C or a dedicated VCO module.
Q: What Arduino library should I use?
Use the Adafruit Si5351 library (available in the Arduino Library Manager). It supports frequency setting on all three outputs, phase offset control, and output enable/disable. For advanced PLL configuration, refer to the Silicon Labs Si5351A datasheet and AN619 application note.
Package Contents
- 1× CJMCU-5351 Si5351A Clock Generator Breakout Module
