Virtex QPRO FPGAs require a certain amount of supply current during power-on to insure proper device operation. The actual current consumed depends upon the power-on ramp rate of the power supply. (This is the time required to reach the nominal power supply voltage of the device from 0 V.) The current is highest at the fastest suggested ramp rate (0 V to nominal voltage in 2 ms) and is lowest at the slowest allowed ramp rate (0 V to nominal voltage in 50 ms).
Devices ordered under SMD (Standard Microcircuit Drawing, B-Grade, Class Q, QPRO and Radiation-Hardened QPRO) or V Grade (QPro Plus, Radiation-Hardened only) parts are tested and screened at -55 C.
The minimum power-on power supply current to guarantee proper device operation for these devices is 2A.
NOTE: Larger currents might result if ramp rates are forced to be faster than 2 ms, or at temperatures below -55 C.
M-grade (Military Ceramic) and N-grade (Military Plastic) parts have not been characterized for the power-up current requirements at -55 C. However, at operating temperatures between -40 C and 0 C, the I-grade power-up current requirements should be applied. At operating temperatures above 0 C, the C-grade power-up current requirements should be applied.
These requirements are available in the Virtex data sheet in the "DC and Switching Characteristics" section (in the "Power-On Power Supply Requirements" section):