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AR# 2745

Ball Grid Array (BGA) Packaging - Which devices utilize the 4x4 ground ball matrix on the BG256?


Keywords: package, packages, BG, ground, 16, matrix, GND

Which Xilinx devices should utilize the 4x4 ground ball matrix on the BG256 package?

To view a drawing of this package, please see the "Package Specifications" page:

Select Standard --> Plastic BGA.

Link to BG256/BGG256 - Package Drawing (Plastic BGA):


As the package drawing notes, only devices with 28K or more logic gates must utilize these extra ground connections. These include:

- XC4028XL and XC4028XLA devices
- Some Virtex devices in the BG256 package

Devices containing 28K or more logic gates will have the 16 extra "thermal" balls. Other devices with fewer than 28K logic gates (such as XC4013XL, XC4020XL, and XC4020XLA devices) will NOT have the 16 extra balls (these are NOT system gates). The XCS40XL device (the largest device in the Spartan-XL family), which has fewer than 28K logic gates, will not contain the extra balls. No Spartan-XL devices have the 4x4 ground ball matrix on the BG256 package.

Note that not all devices with 28K or more logic gates appear on this list (e.g., Virtex-E and Virtex-II). These devices are not offered in the BG256 package.

A BG256 package containing one of the devices listed above will contain the 16 extra ground balls, and these should be connected to the board Ground pin. A BG256 containing any device with fewer than 28K logic gates will not contain the balls. However, for some devices, the ball pads on the package might be present as a gold-plated array without the balls because of potential package-sharing.

The primary purpose of these extra ground connections is to enhance power dissipation in the high gate-count devices.
AR# 2745
Date 04/07/2009
Status Active
Type General Article