Arty S7 DDR3 part and voltage

[catphish]

Hi,

I just got an Arty S7 board, and I'm writing a DDR3 controller. The schematic for this board says that it has a MT41K128M16JT-125:K (a 1.35V DDR3 chip). The manual also states that the DDR3 runs at 1.35V and suggests using 1.35V IO.

However the board I have received contains a PMF511816FBR-KADN. According to its datasheet, this is a 1.5V DDR3 chip.

My initial experiments show that this RAM works, but I am concerned about the voltage mismatch. Please could someone confirm the situation?

Thanks!

[JColvin]

Hi @catphish,

I took a look at the possible build list for the Arty S7 and it seems that the Piecemaker board is a build option for the two versions of the Arty S7, which I was surprised to learn. The datasheet that I am looking at the for the Piecemaker DDR chip (link to datasheet) seems to say in some places that it will work with either voltage (such as in the description on page 4 and page 11) but the list of the parts list on page 5 seems to say only one particular part works on 1.35V.

However, we have one of these Arty S7 boards with that same PMF511816EBR-KADN chip and we verified that it works correctly and measured the capacitors that it runs at 1.35V. I have reached out to our design engineer for this board to confirm this though.

Thank you,
JColvin

[catphish]

Thank you @JColvin,

I'm glad you reached the same conclusions that I did. I can indeed confirm that the memory seems to work correctly at 1.35V, but the datasheet for the DDR chip is certainly ambiguous.

Charlie

[JColvin]

Hi @catphish,

As an update, our design engineer responded back to me saying that they will look into this further since while the part works is nice, having (potentially) operate out of spec is less ideal, so we are learning if that particular component as per the manufacturer specifications can operate at this voltage or not.

Thanks,
JColvin