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Lowering Power using the Voltage Identification Bit

Lowering Power using the Voltage Identification Bit

Voltage identification is a form of adaptive voltage scaling (AVS). The voltage-identification technique described in this application note enables certain devices in the Virtex®-7 family to be operated at a lower voltage of 0.9V while delivering the same specified performance as that of a device operating at the nominal supply voltage of 1.0V. Voltage identification capable devices consume approximately 30% lower worst case (maximum) static power and correspondingly dissipate less heat.

Reduced power consumption is a desirable characteristic and one that Xilinx 7 series FPGAs fulfill in multiple ways. The primary purpose of the voltage-identification technique is to reduce the worst-case power consumption of -1C devices. However, the significance of the voltage-identification technique goes beyond an individual device dissipating less energy, it also can lower the overall system cost.

Power supplies and thermal management requirements are normally specified based on the worst-case power demands of all the system’s components. Although the 7 series FPGAs -1C devices are the most cost-effective, the total cost of a product is the sum of all parts, and costs associated with the power supply and thermal management can be significant. The voltage-identification technique specifically reduces worst-case power consumption, which reduces the overall costs associated with specifying a larger power supply, requiring a heat sink, adding forced air cooling, or including similar devices.

This application note shows the technical aspects of implementing the voltage-identification technique and introduces a reference design for the VC707 evaluation kit. It also explains how voltage identification fits into the complete power portfolio of Virtex-7 FPGAs and highlights the benefits of using the voltage-identification technique to reduce power consumption and system costs.