ADC in Atmega8

I'm not aware of any of the 8-bit AVRs offering that kind of speed, but
there are plenty of pipelined ADC chips that provide these speeds or
faster, and which offer parallel, serial, I2C, and other interface
methods. Try Analog for starters.

-- Gordon

I think you can get up to 0.6Msps with some AVRs (13 ADC clock cycles
per conversion, /2 prescaler for the ADC clock and a 16MHz system
clock). You get a lot of noise running them that fast though, perhaps
effective 6 or 7-bit resolution from the 10-bit ADC. You need to stay
below 15ksps if you want full 10-bit resolution.

I think you'll need an external ADC.


Tim
--
Did I really still have that sig?

On Sun, 30 Apr 2006 18:09:44 +0100, Tim Auton

--snip--

Ignoring all the problems Tim mentions, is there any hope of even
approaching the OP's need for 5Msps by parallelism?

To put it another way, is there any (relatively) simple way of using
multiple AVRs (or other multiplexed ADC chips) together to increase
the effective sampling rate?

I'd guess that synchronization would be a problem. Having (say) 10
AVRs at 0.6Msps all sampling at the exact same instant _does_ yield
6Msps but they're not very _useful_ samples. <grin>  What else would
one have to be worried about?


Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut minds pring dawt cahm (y'all)
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   "Wisdom lies in taking everything with good humor and a grain
    of salt."        -- George Santayana
--

[AVR ADCs]

I'd worry about the low input impedance of multiple AVRs sampling
flat-out; some decent buffering (an op-amp or 10) would likely be
required.

Given 20Msps ADCs cost about the same as just one of the AVRs you'd
need, have higher input impedance, lower noise, and would take about
1/20th the board space, I think one might also have to worry about
ones sanity :)


Tim
--
Did I really still have that sig?

On Mon, 01 May 2006 17:19:47 +0100, Tim Auton

And we haven't even addressed the problem of where to _put_ all those
samples while we're scratching our assets and trying to figure out
what exactly to _do_ with them.

   "All buffers come in one size: too small.


Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut minds pring dawt cahm (y'all)
--
    I would only say to the poets that science must dissect as one
    path to understanding, but never to destroy the beauty and joy of
    wholeness.
    ---
    Stephen Jay Gould / The Hedgehog, the Fox, and the Magister's Pox
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