Has anyone tried running RS-422 directly from a pair, or several parallel pairs, of LVDS I/O’s? Any sucesses?



You can instantiate a differential output driver on the 3005, but if you look at the pin report, it will show the output pins as LVDS25, or possibly some other 2.5 V standard even though the VCCO supplies are 3.3 V. There aren’t any 3.3 V differential output standards on the Spartan-3 E. The Xilinx documents show differential standards supported for input with 3.3 V supplies, but not for output. Nothing will stop you from using differential standards for output with VCCO = 3.3 V, but some things I’ve read assert that it is a bad idea. I’m not sure what the danger is.

If I read the spec correctly, all I need is 20mA, or a differential 2V over 100 ohms… so theoretically it could be done, I was just wondering if anyone had done it successfully…