FPGA + A/D converter

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I am a novoice in FPGAs. My application needs an a/d converter on a FPGA. Is
it possible to design an a/d converter on FPGA. I am using Altera Nios FPGA.
Any info is appreciated.

Thank you,
Srikanth



Re: FPGA + A/D converter
You could make a sigma delta ADC using just the FPGA and a comparator, and a few
r's and c's.  If you use an FPGA with LVDS pin pairs, you might even be able to
use one of the LVDS pairs as the comparator.  Depending on your required sample
rate and resolution, this may or may not be an acceptable hack.  A better
solution for low rate might be to use either an external sigma-delta modulator
or one of the serial ADCs for a minimal added cost system.

Srikanth Anumalla wrote:

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--Ray Andraka, P.E.
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Re: FPGA + A/D converter
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  It all depends on the resolution/speed you need.
Tracking ADCs, which use a DAC and comparitor, are simple.
The DAC can be single pin PWM, or Rate Multiplier - for better
performance, external Vcc/Vref, and buffer all help.
  Gnd and Vcc lines on FPGAs are NOT low noise analog nodes !

  Sigma-Delta ADCs are also simple, but need an integrator/Vref/Slice
for best performance.

  If it is a closed-loop system, where you are more interested in
a balance-point than absolute precision/linearity, then the very
simple single slope RC ramp can be used.
  -jg


Re: FPGA + A/D converter

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FPGA. Is
FPGA.

Any ADC on an FPGA is going to require something externally,
so why not use a cheap external ADC or a small 8 pin micro with an ADC?

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Best Regards,
Ulf Samuelsson   ulf@a-t-m-e-l.com
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