Re: Help to choose the right ADC
- From: Rich Webb <bbew.ar@xxxxxxxxxxxxxxxxxx>
- Date: Fri, 28 Nov 2008 17:25:10 -0500
On Fri, 28 Nov 2008 12:39:42 -0800 (PST), doc.bullwinkle@xxxxxxxxx
wrote:
I'm new about adc, so i need help to choose the right ADC....
i have this signal:
1)signal bandwidth=0-4KHz ==>8ksps min
2)noise free resolution=14bit
other parameters:
1)number of channels:1
2)Vdd=3.3V (preferably)
I'm oriented on sigma-delta adc, but i haven't found adc with this
parameters...Also a sar adc coud be a good choice, but in this case a
greater sps is necessary (i think) to obtain a simple antialiasing
filter....can you help me?
To avoid aliasing into your 14-th bit, you'll need a higher sample rate
in addition to a front-end antialiasing filter.
On the filter side, first, your simplest approach may be one of the
switched capacitor filters from Maxim, Linear, or TI. The corner
frequency can be tuned with an external capacitor or external clock (for
a more stable response).
<http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=MAX7414EUA%2B-ND>
is one possibility among many. Some are available in DIP, if that's
easier to use. Other options, of course, including roll yer own.
On the sample rate side, a 5-th order filter would require you to sample
at about 60 Ksps in order to put Nyquist about 84 dB down and prevent
higher frequency signals from being aliased back into the passband at an
amplitude that will show up in the 14-th bit.
--
Rich Webb Norfolk, VA
.
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