Analog Front End or ADC with FPGA

[dmorris619]

Let me preface this by saying I am very new to FPGA's.

I am trying to find a way to sample 3 channels simultaneously at a resolution of 16 bits per channel and at a rate of at least 600KSPS per channel and then 2 channels at a resolution of 16 bits at a rate of at least 200KSPS. I've decided on using an FPGA and am now looking at what will convert the analog signal into digital signals.

My largest problem is that I do not have the time to create a custom pcb that contains the discrete ADCs and the FPGA on one board. So I have been searching high an low for an FPGA dev board that contains adcs that meet my specs. Since I've been unable to locate such a dev board I'm thinking about the possibility of locating an external board that contains the adcs I need and then interfacing that to a standard fpga dev board. I still haven't had much luck in this area either, but then again I really don't know what I'm looking for in terms of names/terminology.

I have located some HSMC boards that have analog front ends, but I don't think I want to use an analog front end because I am already amplifying the signal and then low pass filtering it. I really would like to find a mezzanine card that just has analog to digital converters on them.

Any help would be greatly appreciated.

 

[Fish4Fun]

I have no idea what parameters are important to you beyond the stated 3 channels @ 600 KSPS + 2 Channels @ 200 KSPS, but if COST is a consideration and you really NEED 16 bit resolution, then you will ultimately have to consider using a single ADC @ > 4 MSPS, and "switching" between analog inputs versus 4 or 5 discrete ADCs. Switching between inputs obviously will have its own problems and will place the samples 250nS apart, if this is satisfactory it will be considerably cheaper than 5 discrete ADCs. Depending on the depth of the data acquisitions, you may have to give careful consideration to the digital side of the project. Acquiring 1 second worth of data @ 4 MSPS X 16 bits is 8 MB/s and can be a non-trivial portion of the project even w/o considering processing the data.

Ti has a 4MSPS Devboard for their ADS8422,

http://focus.ti.com/lit/ug/slau192/slau192.pdf

IF you want true simplicity, you might consider looking @ the 16-bit versions of something like:

http://www.picotech.com/oscilloscope-specifications.html

Two or three of these could easily achieve your goals with plug-n-play ease, though finding a PC that can handle the throughput simultaneously could prove problematic.

If 16 bit resolution is not truly requisite then the project gets easier and cheaper as the number of bits decreases. I am sure you are aware that 16 bit resolution gives you roughly 150uV steps @ 10V while 8 bit gives you only 40mV steps @ 10V. The real problem as you increase resolution becomes accuracy. Achieving accurate linear analog amplification and reference is fairly easy with 8 bit resolution but becomes increasingly difficult as you move toward 16 bit resolution.

Anyway, Good Luck!

Fish