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Altera_Forum
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12 years ago

Cyclone IV IO bank power sequencing

I have a Cyclone IV device as a managment device for the balance of circuitry on a board. The FPGA comes up prior to much of the rest of the board being powered. The FPGA will be responsible for sequ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

Hi Dave, thanks for your thoughts.

I have a DE2-115 dev board. However, whilst the jumpers for the bank voltages can be removed, that doesn't disconnect power from the associated bank. It simply sets it to a default value - 3.3V.

I do have an alternative board that I could try this on. Given the hot swap features Altera promote with this family I would expect this to work. However, there is a difference between it working on a few boards and Altera clearly stating that this is a supported feature of Cyclone IV devices.

I do like your suggestion of using some form of power switch for different portions of circuitry. The only hurdle here is the on resistance of such a switch. The one you've identified is not up to my requirements (possibly up to 1Amp). However, the principle is good. A P-channel FET with a low on resistance may suffice.

It may also be possible to boost the 1.8V rail a little such that any voltage drop through the high side FET is negated and the other circuitry remains within spec (+/-5%). The Cyclone IV would be happy to operate at 1.8V+5%.

Cheers