GrantXTV wrote:In this application it lets me set the video bandwidth before the ADC, by changing the clock frequency at a ratio of 50:1, say if you wanted to change to a different video mode for example. Grant
Yes, they seem to be the answer where you want variable cut-off frequency filters - just change the clock frequency - done! With SSTV there's little reason to alter the cut-off frequency, so that's not the reason to consider them here. But in terms of board space (quantity of components), cost and 8th order filtering as opposed to 4th, they're ideal. A single chip as opposed to two op-amps, four resistors, four capacitors with their tolerances and lack of easy change in cut-off frequency...a powerful incentive to use them. The only downside is providing the required clock signal, though that's usually not a big issue, besides, they have an internal clock oscillator anyway!
Steve A.
P.S. This is not a commercial! PDF follows for those interested....