Reminds me of one of my first major designs as a young 'un, a vehicle loop detector that was used in Western Australia for 15 years. The best compnent I had to work with was an LM308, which had sufficiently low input bias current to let me make a differentiator with a time constant of 10 seconds or so. The differentiator was to pick out small changes (0.3%) in the loop impedance with very low rates of change (i.e. slow moving cars).
Our competition (Eagle Signals) used a resonant loop (like TI's chip) in an AGC'd oscillator circuit, and a partially charged NiCd cell for the long time constant. I avoided resonant/oscillator schemes because of fierce interaction between adjacent loops, and opted instead for a forced loop drive with the same master oscillator driving them all.
It would be fun to make a loop detector with this new chip. Interesting it's not mentioned as a possible application. Maybe it's not got enough input protection? A lighning strike near a detector loop can ruin your day!
Pretty cool stuff!! TI is getting stronger in the analog domain with this kind of cool innovative products. I think there could be many promising ideas of using this device. The simplest one that occurs to me (which I would like to try) is making a cheapest, smallest metal detector gadget for fun. :)
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