Connecting a fast ADC to Alchitry boards

General
1

Hello guys!

I am planning a project where I need to read an 14-bit ADC with four simultaneously sampled channels at 25 MSPS. The ADC output is LVDS 1.8V, two pairs for each channel.

  1. I would like to ask you if the ICE40 can handle this amount of data? Is it fast enough?
  2. Can I connect a board with such ADC using a cable, to the BR board, where I would solder a pin header?
  3. From the ICE40 application note I understood that the LVDS pairs have to be terminated with 100 ohm resistors. I assume these resistors do not exist on the CU board. Can I solder them on the BR board? Will this be close enough?
    I will of course try to use a short cable.
  4. If I use the AU board will I need any soldering of termination resistors or the Artix7 has it built in?

I appreciate any tips to help me decide if using the CU board and in general the ICE40HX FPGA makes sense or I should look for something more powerful.

I have the AU board and I am thinking of buying the CU because it would be a perfect small FPGA companion for the STM32H7 that I plan to use, if only it can work.

Thank you!

2

From what I can glean from the data sheet LVDS for the ICE40 HX requires VCCIO to be 1.8V. The Cu has this fixed at 3.3V.

The Au can accept 2.5V LVDS inputs on banks with 3.3V VCCIO but none of the banks on the Au’s FPGA are rated for 1.8V LVDS (HP vs HR, Au only has HR banks).

The Au is currently undergoing a revision update to make the switchable voltage between 3.3V and 2.5V instead of 1.8V to enable 2.5V LVDS outputs. See page 91 of this document for move LVDS info.

The Au has built in termination but it can’t be used unless VCCIO is 2.5V (for 2.5V LVDS). If you’re interested, I can ping SparkFun for when they think the revised board with 2.5V will be available.