1. Home
  2. Electronics Design
  3. Help to choose the right ADC

Help to choose the right ADC

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? Thanks in advance
Reply to
doc.bullwinkle
Loading thread data ...

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).

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
Reply to
Rich Webb

That's a vast oversimplification. See

formatting link

Another simplification. You'll never be entirely free of noise -- you can only hope for a region where noise is vastly unlikely to penetrate.

But it's not as bad as #1.

There are some S-D converters that are designed for 60Hz cutoff that can be yanked around to higher output sample rates, but I don't know if you can get by with 3.3V, and I don't know if they can be yanked up to 8ksps.

Beware: there are also S-D converters that work over time intervals, so they alias with the best of them (see TI's 'F2013 and it's ADC).

If you've got the computing power, why not use a SAR, oversample, filter and decimate? It should be easy to find a SAR converter that does what you want, absent free anti-aliasing.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
Reply to
Tim Wescott

Thanks for infos, but i have a new question:how to simulate it?With your help, i've chosen an sar adc from linear technology....but i don't kow know to simulate it (if possible) with spice. I've downloaded from website pspice library, but i haven't found any adc (perhaps i'm wrong)....i've downloaded ltspice, but nothing i've found...It's the first time that i use an adc, so can you help me? Thanks

Reply to
doc.bullwinkle

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.