22.214.171.124. I/O Simultaneous Switching Noise
|1||Reduce the number of pins that switch the voltage level at exactly the same time whenever possible.|
|2||Use differential I/O standards and lower-voltage standards for high-switching I/Os.|
|3||Use lower drive strengths for high-switching I/Os. The default drive strength setting might be higher than your design requires.|
|4||Reduce the number of simultaneously switching output pins within each bank. Spread output pins across multiple banks if possible.|
|5||Spread switching I/Os evenly throughout the bank to reduce the number of aggressors in a given area to reduce SSN (when bank usage is substantially below 100%).|
|6||Separate simultaneously switching pins from input pins that are susceptible to SSN.|
|7||Place important clock and asynchronous control signals near ground signals and away from large switching buses.|
|8||Avoid using I/O pins one or two pins away from PLL power supply pins for high-switching or high-drive strength pins.|
|9||Use staggered output delays to shift the output signals through time, or use adjustable slew rate settings.|
SSN is a concern when too many I/Os (in close proximity) change voltage levels at the same time. Plan the I/O and clock connections according to the recommendations.
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