FPGA Cyclone V power from single DC/DC chip

Altera_Forum · ‎08-20-2016

I want to ask about the best power circuit for powering a Cyclone V chip.

I don't mean a specific chip number, but I am concerned about how to generate all the supplies required.

For all last designs I participated in, or found online on evaluation boards, an independent supply is used for each voltage required. For example the chip requires the following voltages:

1.1V for the core and the HPS

2.5V for soe other supplies like the VCC_AUX

3V for VCCIO and other chips on the system

Evaluation boards use a separate DC/DC or LDO for each voltage required. Here comes my question, won't it be easier to use a single chip which can generate 4 independent voltage outputs to drive the FPGA? Is there any problem in such a solution?

I found some DC/DC from analog devices and other companies that can generate up to 4 outputs ranging from 1 or less volts to 5V.

What is the best approach when I am limited in the board space?

Altera_Forum · ‎08-20-2016

I'm a software guy so this may be wrong. Altera has a line of power supply chips designed for their FPGAs. I think they are so expensive that designers mostly don't use them unless board space is more important than cost. I think they have long lead times and aren't available in small quantities as well.

Altera_Forum · ‎08-20-2016

Galfonz - Are you talking about the Enpirion parts? We use a lot of them and although I'm not involved in purchasing I don't think we've ever had any lead time problems, and we would not be using them if they were not price-competitive with Linear, TI, Analog, etc.

sherif123 - There should be no inherent reason that you can't use a single chip that produces multiple rails. Just make sure the multi-rail chip meets all the current and sequencing requirements from Altera. The parts from Analog Devices look pretty nice but they require external inductors and other components. Those components can take up a lot of board space, and regulators with external inductors usually have very specific and careful layout requirements. The nice thing about the Enpirion parts is that they have no external inductors. Makes them very easy to use. Obviously some trade-offs here, but you need to look at the total solution before you assume that the single 4-rail Analog Devices chip will be smaller (and/or cheaper) than multiple 1-rail parts.

Altera_Forum · ‎08-21-2016

rsefton, thanks for your reply.

I did not use Enpirion parts before and did not use the single 4-rail Analog Devices chip before. So the both solutions are new to me.

Yes the analog devices parts require external inductors and thank you for making me notice this.

I will study both solutions for area and cost.

Thanks