What is the Power-on-Reset (POR) threshold voltage?
The Virtex-II/Pro internal Power-on-Reset (POR) circuit is triggered when the following conditions are met:
VCCAUX > 2.5V
VCCO (Bank 4) > 1.5V
Vccint > 1.2V
Vccaux > 1.9V
Vcco > 1.4V
At power up, the device requires the VCCINT power supply to monotonically rise from 0V to nominal voltage (1.5V) within the specified VCCINT rise time. If the power supply cannot meet this requirement, the device might not perform POR properly.
If the device is in operation and one of the supplies is lost, the DONE pin must be checked to show that configuration has been lost. Then, if all the POR conditions are met, the device will reconfigure. If configuration is not lost, the previous configuration will be retained.
Please see the Virtex-II data sheet and user guide for additional details at: