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AR# 57775

2014.3 Vivado Power - Why is the power consumption of an FPGA device not published in Xilinx documents? How can I find the power consumption of an FPGA? How can I estimate the junction temperature of my design in an FPGA?

Description

Why is the power consumption of an FPGA device not published in Xilinx documents?

How can I find the power consumption of an FPGA?

How can I estimate the junction temperature of my design in an FPGA?

Note: This article is part of Power Solution Center.

Solution

Unlike ASIC, in an FPGA device everything (IP cores, logic, IO standard, drive strength etc. all) is programmable.

As a result, Xilinx does not include power consumption in documents because it is mostly dependent on user design (Code), not the device part number.

However to estimate the power in your FPGA, Xilinx does provide a complete solution that encompasses power estimators and analyzers, and power-driven implementation tool algorithms.
There are two types of power tools available to estimate the power for FPGA devices.

XPE (Xilinx Power Estimator)
and
Xilinx Power Analyzer (for use with ISE tools) / Report Power (for use Vivado tools).

XILINX Power Estimator (XPE) helps you to roughly estimate the power before implementing the design in XPE.
This allows you to roughly estimate the power supply and board size.

XPE spread sheets are provided in the following Xilinx web site link

http://www.xilinx.com/products/design_resources/power_central .

Here you can download required device XPE Spreadsheets.

Please note that you will need to have a Xilinx free membership account to download.
You will also be required to sign the online license agreement.

After downloading the spread sheet, you will need to update all of the estimated resources entries like clock, logic, IO, BRAM, DCM, etc. to match the requirements of your design.

After properly updating all of the resources, you can see all of the power supply rails approximate consumption & estimated junction temperature details in the summary page.

The accuracy of power estimation depends on the user estimated resources entries in all XPE pages.

The necessary instruction and guidelines to use the XPE spread sheet can be found in (UG440):

http://www.xilinx.com/products/design_resources/power_central/ug440.pdf .

An example XPE summary page for a Virtex-7 FPGA is shown below.

Estimated junction temperature is also shown here:

The Xilinx Power Analyzer (XPA) tool which can be generated ISE Design Suite helps with accurate power analysis after a design has been implemented successfully.

XPA estimation is more accurate than XPE because the XPA takes all resource entries directly from the user design files, apart from some environment entries.

In Vivado Design Suite, the XPA report is called "Report Power".

Instructions and guidelines on using XPA/Report power can be found in the tools help documentation.

The following screen capture shows how to generate "Report Power" in Vivado:

The below screen capture shows an example summary report page in "Report Power".

The estimated junction temperature and allowable thermal margin for that design are also shown in the report: