Hi, I have to acquire 9 couples of differential signals inside my Spartan3 fpga. How should I handle them? Should i use IBUFDS (with I and IB as true and inverted inputs, while O as my "decoded" output)? Is it 2.5V (with the inverted being -2.5V) the maximum allowed differential input voltage with XC3S200 FT256? Thanks, Marco
"Marco" schrieb im Newsbeitrag news: snipped-for-privacy@f14g2000cwb.googlegroups.com...
basically yes
S3 doesnt allow any more 3.3V differential outputs, but for inputs I think 3.3V LVDS is still supported. just try out if not the tools will throw an error
ah, there is no -2.5 of course, the inputs + and - should be in some allowed common mode DC range from somewhere inbetween 0 and 2.5V, swinging around the common mode voltage a few hundred millivolts
-- Antti Lukats http://www.xilant.com
Antti, thanks, sorry for the -2.5V, my fault! I searched on the Spartan3 data sheet and on table 10, pag.10 of DS099-3 there seem to be only 2.5V allowed, no 3.3V. Marco
We run LVDS inputs on S3's with Vccio = 3.3 (actually, 3.6 sometimes!) and it works fine. Common mode range is damn near rail-to-rail. The LVDS inputs are excellent comparators.
John
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