 |
|
|
|
|
Maxim >
Products >
Clock Generation and Distribution
|
|
|
Clock-Tree Integration Saves Money, Space, and Power
With the advent of multi-output programmable clock generators, clock trees can be integrated into fewer devices. Elimination of components saves board space, reduces power, and saves money.
Packaging is the fundamental enabler.
- Oscillator modules provide only one output because 5mm x 7mm ceramic packages have just 6 pins. Traditional clock trees based on oscillator modules require separate fanout buffers to provide multiple outputs.
- Clock Generator ICs can be packaged in various sizes with lots of pins. The larger pin count allows fanout buffers to be integrated with clock generators. In addition, clock generators can be programmable and can synthesize multiple clock frequencies from a common crystal, thus replacing multiple oscillator modules.
PLL technology enables elimination of clock tolerance compensation circuits.
- Oscillator modules typically have frequency tolerances of ±50ppm. ASICs running from multiple related clock frequencies, for example 312.5MHz and 156.25MHz, will see slight frequency differences between the two clock domains, in this case up to ±100ppm. To compensate for these differences, ASICs include FIFO-based clock tolerance compensation circuits.
- Clock generators can derive multiple harmonically related frequencies from a single crystal with zero error between clock domains, eliminating the need for clock tolerance circuits in ASICs.
Maxim Clock-Tree Solutions
For examples of clock trees implemented with Maxim clock generators, please see:
View a parametric table of clock generator ICs with:
To build large clock trees, the most economical solution is a combination of clock generators and fanout buffers. Maxim has a broad family of LVPECL and LVDS fanout buffers with numbers of outputs ranging from 2 to 15.
For more information:
- Fanout Buffers: Maxim's economical fanout buffers have excellent performance and contribute virtually zero jitter to clock trees.
- Fanout Devices with Synthesis and/or Division: For multiple harmonically related frequencies, Maxim has specialty fanout devices. The MAX9322 integrates frequency division and provides 15 outputs. The MAX3671 and MAX3673 integrate frequency synthesis and provide 9 outputs.
|
|
|
|
