That circuit on P. 16 of the app note isn't just a lowpass filter--it's
AC-coupled at the input. That's why it needs its own bias resistors.
A plain-vanilla Sallen-Key lowpass is a DC-coupled noninverting
amplifier with unity DC gain, making it a reasonable choice for
antialiasing. Its output basically just follows its input, so you
shouldn't need a separate source of bias.
You do need to pay attention to what happens to the op amp's output
impedance at high frequency, though. "Rail-to-rail" outputs are
intrinsically high impedance, and rely on feedback to get low
closed-loop output impedance. (LDO regulators have the same issue, for
the same reason.) That means that the op amp's output impedance rises
more or less linearly with frequency, i.e. it looks like a lossy
inductor. At some frequency that will mess up your filter
characteristic, so you need to calculate it fairly carefully.
Some RRIO amps (e.g. the AD8605) use fast internal feedback around the
output stage, which makes them quite a bit stiffer. Those ones make
much better ADC drivers as well as better filters, compared with
normal RRIO amps.
If you use an amp with totem-pole outputs, you'll need that charge pump
to get the output to swing to ground, but with an RRIO with stiff
outputs, you should be able to get away without it.
One very useful tip is to make sure that you have a small positive
offset, i.e. that zero signal gives you an on-scale reading from the ADC.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058
hobbs at electrooptical dot net
http://electrooptical.net