Judge the Chip by Its Cover
Go Ahead
Packaging is one of those areas where everyone really wants the same thing, which is a package with just enough I/Os to fit their design in the smallest footprint possible at the lowest cost. So basically everyone wants or needs a custom package.
Actel has delivered all the standard packaging you would expect to see for FPGAs, with plenty of variations of I/O count, power consumption, and performance. Then on all sides of the standard packages, Actel has gone to extremes to meet the needs of an engineer who is designing beyond the standard FPGA limits. As you read this, be aware that this is only part of the story. We're not done yet.
Minimizing Footprint for Real Designs
Actel offers a µCS81 package for IGLOO devices. This package is 4x4 mm with 0.4 mm pitch. There are no other CPLDs or FPGAs that offer this packaging technology. Now, in a 4x4 footprint, you would assume that you don't have many user I/Os, but since the pitch is 0.4 mm, there is room for plenty of I/Os as well. Compare this at low density with MAX IIZ CPLDs of comparable size.
| Footprint | User I/Os | Package Pins | Technology | Pitch | |
|---|---|---|---|---|---|
| AGL030 | 4x4 mm | 66 | 81 | Micro Chip Scale | 0.4 mm |
| EPM240Z | 5x5 mm | 54 | 64 | Micro FineLine BGA | 0.5 mm |
The only small footprint package CoolRunner-II has is 5x5 mm with only 21 I/Os, supported only in their smallest density—about one-eighth the logic of AGL030—so it isn't really competitive in the same field as these two. The device that is comparable in logic to the two above comes in an 8x8 mm package, which has a footprint 4 times larger.
Maximizing Number of I/Os per Board Area
In the mid-range density devices, the CS196 package offers an 8x8 mm footprint with up to 143 user I/Os, and the CS281 offers up to 215 I/Os in a 10x10 mm footprint. For Spartan-3 (all family variations), the maximum number of I/Os in an 8x8 mm area is 92. The next smallest package size is 16x16 mm, which has 64 user I/Os. Altera does slightly better with a 14x14 mm package with 182 user I/Os. Neither vendor has chosen to address the needs of designers looking for smaller-footprint, higher-I/O packages, which are required to meet the needs of the aggressively competitive market that designers face.
Migration and Flexibility
Just in case you decide to start with a ProASIC3 device, and then decide maybe you should have used an IGLOO device for lower power, Actel also offers many packages that allow migration—not only within each family but also across multiple families, including ProASIC3, IGLOO, and the new ProASIC3L family. Refer to device handbooks on the Actel website for migration tables.
Actel has firmly established itself as the leader in innovative packaging for programmable logic to meet the demands of small-form-factor, battery-powered devices that are exploding across rapidly changing applications.
