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Altera_Forum
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10 years ago

Cyclone II LVDS termination on DE2

hey guys, I the plan is to use the Terasic DE2 LVDS lines to receive serial data from an ADC. The Cyclone II device handbook (figure 11-3) says that the LVDS receiver line should terminate with...
Altera_Forum's avatar
Altera_Forum
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10 years ago

The skew between the traces on the DE2 board shouldn't be enough to cause you trouble at those rates.

At 720Mbps you've a 1.4ns period. LVDS requires a transition time - the only thing trace length mismatch is going to have a negative impact on - of between 260ps and 0.3 * 1.4ns = 417ps. Typically devices will operate nearer the higher end of that range to keep switching noise to a minimum.

Trace length mismatch can probably 'eat into' half of that - 417ps/2 (and probably more) - before you notice any adverse effects. That's well over an inch of extra trace on one of the pairs with respect to the other. I'm sure you will be able to find one (or more) pairs that fit that criteria.

If you do run into trouble reduce the clock rate. You should find the transition times increase and help you out.

Cheers,

Alex