DAA suggestions

History books? It is a good many years since I have seen a fax, and even longer since I have dealt with modems.

More seriously, I'd look for some ready-made modem modules, and then look at their application notes and reference designs for the line interface.

I'm not sure whether you're after specifications or parts / design ideas, but give this a try for some example parts:

Regards, Allan

I just checked the price: ~$10 at Digikey for an Si3018. Ouch. I guess it does include isolation and replaces the entire line hybrid though.

I can remember having to do that with transformers "back in the day."

Allan

TI has a bunch of app notes. You'll find them in the softmodem (DSP) app notes.

Cheers

Make sure the parts you select work 100% in your application before you commit to them. Years ago I used a CP Clare pair of chips (or maybe it was three) for a DAA function. The chip that did the signalling was not designed to come up in any particular state and couldn't retain it's programming while the line was on hook. But the real gotcha was the chip with the analog interface has 0dB of PSRR. Yes! ZERO dB. If I had 10 mV of noise on the power bus, I had 10 mV of noise on the line which could be heard.

Get an eval board and check out the devices thoroughly.

Yes, I've been rummaging through *old* 320 app notes. More modern notes seem to just "give solutions" whereas the older ones seem to give *explanations*. (I want to understand *why* particular design choices were made in the pp note/reference design and not just embrace the author's unwritten assumptions!)

I was just looking through some old Radio Electonic mags, lost of telco projects, might get some info there too.

Cheers