Answers Database
Virtex-E: Can we tie Vcco to 2.5 V for LVDS, and have LVTTL inputs?
Record #8432
Problem Title:
Virtex-E: Can we tie Vcco to 2.5 V for LVDS, and have LVTTL inputs?
Problem Description:
Urgency: standard
General Description:
Virtex-E: Can we tie Vcco to 2.5 V for LVDS, and have LVTTL inputs?
Solution 1:
For all single-ended IO standards in Virtex-E the input pad has a clamp
diode to VCCO. In this case it would be 2.5V. If the IO is driven to 3.3V
it will cause too much current to flow through the clamp diode to the VCCO
rail at 2.5V. A 100 ohm resistor will need to be inserted in series before
the pad to limit the current to acceptable ranges.
This is similar to what is shown on our web page; except the input voltage is
at 5V. See end of table 1 on http://www.xilinx.com/products/virtex.htm
See note on the page mentioned:
*** Requires 100 Ohm external resistor for Virtex-E family
End of Record #8432 - Last Modified: 01/20/00 16:16 |
