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Altera_Forum
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18 years ago

Measuring SSN

Hi, i have seen people trying to measure SSN with the toggling aggressors on the FPGA floating (not connected to anywhere). How accurate is that compared to aggressors with load?
Altera_Forum's avatar
Altera_Forum
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18 years ago

One effect that load caps have is reducing the amount of SSN seen at the far-end. If you toggle a bunch of aggressors and want to know whether the noise seen on a victim pin will result in a spurious far-end toggle, then you definitely need to include load caps. The load cap (or far-end chip) will serve as a low-pass filter, and thus reduce the magnitude of the peak noise event seen by the far-end device.

Bottom line: SSN is very complicated. You need to measure the SSN in your real system if possible, since the board thickness, I/O standards, loading, trace, far-end load, PDN decoupling, and even the oscilliscope and probing technique you use will all influence the magnitude of the noise you measure.

Regards,

Paul Leventis

Altera Corp.