[SI-LIST] : Termination scheme for SSTL2 Class II

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From: selvaraj subramanian (selvaraj.manian@wipro.com)
Date: Mon Feb 26 2001 - 03:36:16 PST


Hello,

I am having SSTL2 Class II logic in my design. As per the standard, a series termination of 25ohms and a pull up value of 25ohms to 1.25V at the far end is recommended when the characteristic impedance is 50ohms. I am simulating bidirectional (data) SSTL2 Class II lines. But my simulation using XTK is not showing correct waveforms. But if I use a double termination scheme of 25 ohms series termination and a pull up value of 50ohms to 1.25V at both the ends (near & far), the simulation is showing the expected results.

But my doubt is that if the driver is bidirectional, is it compulsory to use double termination scheme?.

If anybody has worked in this, please let me know which one is correct and if not let me know the correct scheme.

Thanks in advance.

regards,

Selva
Wipro Technologies,
Bangalore, India.

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