A7-FTG256: Decoupling caps on unused banks

[rgc_]

Hi folks,

I have an A7-FTG256 based design in which every penny and mm2 of board is relevant. I managed to get the IOs under 100, so I can make them fit in two banks out of the 3.5 banks in the package.

The UG483 indicates how to maximize ESD protection in unused banks, and so I did. What is not specified, and I just assumed, is that I can remove also the decoupling caps for the unused banks from the design.

Is this OK? anyone have done that already?

Thanks in advance.

[asmi]

Yes you can.

Also, if you want to shave a bit more off PCB area and cost, you might want to consider using Spartan-7 instead of Artix-7. They are available in smaller 15x15 mm 196 ball package which has 100 I/O balls, so it should be a better fit for your needs. S7 has a bit less of DSPs that equivalent A7, but otherwise they are pretty much the same (sans MGTs of course, but FTG256 package doesn't bond out any, so it's a wash).

[rgc_]

Thanks asmi, much appreciated.

Thanks for the heads-up on the S7, too. Unluckily (and strangely) there's no S35 part, and the design wouldn't fit on an S25. That makes the A35 the less expensive part available for the project.

[NorthGuy]

That makes the A35 the less expensive part available for the project.

How do you determine the price when it is not sold anywhere?

[rgc_]

Distributors will usually give you a quotation, even when there's no stock. It is true that price ratio in between devices of the same family sometimes change, but I haven't seen too much of a change for the S7/A7 series in a few years, specially in high volumes where prices are nothing like in DK listings.

While that doesn't work for setting final product/contract pricings, it does work for picking up devices for new designs.

[NorthGuy]

Distributors will usually give you a quotation, even when there's no stock.

The price is useless when there's no stock. The prices will be different when (if?) new stock emerges.

[rgc_]

Prices will most likely be different, but that is irrelevant for the device selection as long as all devices of a given brand/series are changed by a more-or-less similar %, and this is what happens in most cases in our experience.