Modern 4K and 8K video processors often integrate multiple high-speed interfaces and subsystems on a single FPGA-based board. These may include SDI and HDMI 2.1 transceivers, DDR frame buffers, multiple Ethernet ports, audio codecs, and MCU peripherals.
Each subsystem requires a specific clock frequency. If these clocks come from unrelated sources, frequency and phase differences may increase synchronization complexity and contribute to unstable video, interface errors, or audio-video synchronization problems.
A traditional design may use several fixed-frequency oscillators to supply different subsystems. Although straightforward, this approach introduces several drawbacks:
The SYKG1042E (Q5) multi-channel PLL clock generator offers an alternative. Using one reference crystal, it can generate four configurable clock outputs for different devices on the same board.
The SYKG1042E (Q5) supports 25 MHz and 50 MHz standard reference crystals, as well as custom input frequencies such as 24 MHz.
Its main capabilities include:
These capabilities allow the device to supply clocks to FPGAs, SDI interfaces, high-speed Ethernet PHYs, audio codecs, MCUs, and other peripherals.
In this FPGA-based video-processing design, a high-precision 25 MHz crystal provides the reference clock for the SYKG1042E (Q5).
The internal PLL generates a high-frequency VCO signal, which is then divided through independent output channels. This allows multiple subsystems to receive application-specific frequencies derived from the same reference source.
| Channel | Output Frequency | Target Module |
|---|---|---|
| OUT0 | 122.88 MHz | FPGA and SDI/HDMI video path |
| OUT1 | 156.25 MHz | FPGA DDR image buffer |
| OUT2 | 125 MHz | Multiple Ethernet PHYs |
| OUT3 | 50 MHz | Downstream clock generator |
Whenever possible, a 25 MHz or 50 MHz reference crystal should be selected. These frequencies make it easier to generate multiple outputs through integer division, which generally provides better jitter performance. Fractional division can still be used for channels requiring special frequency combinations.
Deriving multiple clocks from one reference source reduces asynchronous clock relationships between subsystems. This can simplify synchronization and help prevent display artifacts, link errors, and audio-video timing issues.
One clock generator and one reference crystal can replace multiple fixed-frequency oscillators, reducing BOM complexity and PCB area.
FFB integer mode provides lower-jitter clock generation for high-speed video interfaces such as SDI and HDMI 2.1.
I²C configuration allows one hardware platform to support different video formats and operating modes without changing the physical clock components.
Built-in spread-spectrum clocking can reduce peak emissions and help lower the effort required during EMC debugging and system certification.
This clock architecture is suitable for:
By consolidating multiple clock frequencies into a single configurable device, the SYKG1042E (Q5) helps simplify clock-tree design while improving system flexibility and synchronization.
