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What is it? Creltek 8 Channel Clock Generator v1.1 The Creltek 8 Channel Clock Generator provides up to eight independent PLL-synthesized clock outputs. The Silicon Labs Si5351A chip used on this...Read More…
The Creltek 8 Channel Clock Generator provides up to eight independent PLL-synthesized clock outputs. The Silicon Labs Si5351A chip used on this board is capable of generating clock signals from less than 8 kHz to more than 160 MHz. Almost any exact frequency can be programmed, and although different frequencies on multiple outputs must be mathematically related, the flexible "multisynth" architecture allows many useful combinations to be achieved. Outputs feature low jitter and glitch-free frequency changes.
Generated frequencies can be arbitrary and non-integer-related, and all outputs share a common time domain (outputs will not "drift" relative to each other). This is similar to (and compatible with) other Si5351A-based clock generator modules out there, but offers 8 outputs instead of 3, and comes in a 24-position, 0.5"-wide DIP-style package which is perfect for solderless breadboard or prototyping use. All necessary support components are included on-board, including a 25 MHz, 30 ppm stability clock crystal (a 10 ppm, 25 MHz or 27 MHz crystal is available as an option at checkout). Care has been taken to optimize component layout and trace routing in order to minimize noise and interference.
Machined pin headers are available as an option at checkout.
The Creltek 8 Channel Clock Generator operates on a single 2.5V or 3.3V supply and all I/O pins are specified for 3.3V CMOS logic levels maximum. *Note: while the clock outputs can drive most 5V-level devices, the inputs to the Creltek 8 Channel Clock Generator must NOT be connected to 5V signal levels; they are not to exceed the supply voltage.
The device is programmed using commands over an I2C (two-wire) bus. (Solder pads are provided for optional 0805-size pull-up resistors if you wish to terminate the I2C bus on the board; however, these are not needed if your I2C bus is terminated elsewhere.) A variety of libraries for programming the Si5351A are available on the internet. The EtherKit Si5351 Arduino Library is a good place to start, and supports programming all 8 outputs and a number of other useful features.
The Si5351A has a register that can be programmed to provide the desired crystal load capacitance. The setting for "10 pF" should be used all crystals currently offered.
The appropriate I2C register settings (which include PLL and "multisynth" multipliers/dividers) can also be easily calculated using one of the "ClockBuilder" tools from Silicon Labs:
Silicon Labs ClockBuilder (via Adafruit) - Windows Installer
Silicon Labs ClockBuilder Pro - Windows Installer (requires free registration on Silicon Labs' website)
The on-board crystal drives two internal PLLs which can be independently programed (via a multiplier) to frequencies between 600 and 900 MHz. This high-frequency internal signal is then divided down to produce the desired clock outputs. The last two outputs divide down by a simple programmable integer. The first six outputs utilize a flexible fractional division block, which Silicon Labs calls a "multisynth". The multisynth architecture allows a wide array of arbitrary and exact frequencies to be achieved. A fixed (but limited) phase offset can also be programmed on each output.
The dividers for each output can be driven by your choice of either of the two internal PLLs. Outputs can also be individually enabled, or disabled and placed in a high, low, or open state. Additionally, the crystal oscillator signal can be mirrored directly to any desired outputs. Pairs of output drivers can also be shut down to reduce energy usage.
Pin 12 - 3v3 (positive power supply)
Pin 13 - Output 1
Pin functions are silkscreened on the top of the board for easy reference.
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I'm an avid electronics hobbyist and a talented programmer with a passion for creative problem-solving, design, and systems integration. As a member of the Creltek design group, I enjoy finding elegant solutions to complex problems, and combining hardware and software in new and unique ways. I maintain an extremely wide range of interests, and strive to stay on the cutting edge through constant innovation and application, both at work and during personal pursuit in my free time.
My current electronics research includes LED lighting, resonant high-frequency switching power supplies, embedded systems, multi-core microcontrollers, digital audio and MIDI, and the design of reusable circuit modules for rapid prototyping, research, and development.
My day job involves managing the IT department and teaching at a small private college. You can check out my LinkedIn profile here: https://www.linkedin.com/in/kevpatt
Creltek is a private technology design group engaged in innovative software and hardware integration, research, and development. We strive for high quality and excellence by design. When a member of our engineering team creates a module or tool that might be useful to others, we try to make it available here on Tindie!
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