80MHz single-ended receiver

What about using a BUF602 again at the receiving end? Look at the application note in the datasheet, on the first page. Replace the 2k resistor with 50 Ohm and use a 1:1 transformer parallel to the resistor to couple the signal from the coax. If you need some gain, use a standard 1:4 balun and use 200 Ohm.

Meindert

I probably should have mentioned that I need to stay DC-coupled. I'm provided with clock and data lines, and there is no guarantee of regular transitions on the data line.

Right now I'm pressing ahead with an LVDS-based design. It should work, but seems kludgey .

Thanks for the suggestion, though.

Steve

Ah, yes :-)

regular

At what distance/attenuation does it have to work on? If you terminate the coax at the receiving end, couldn't you still use a BUF602 as receiver, use the same circuit but without the input cap?

Meindert

The (incomplete) data I've been given is that the signal develops around

1.7V across 50R at the receiver. This makes sense from a DC point of view (50R source, 3.3V power, 50R receiver), but implies that there is no significant attenuation along the cable. I'm not sure I can depend on this, so my design has to tolerate a smaller swing at the receiver.

Re using a BUF602 as a receiver: I did consider this to start with, but reading the datasheet I didn't get the impression it would do much for me. It seems to be characterised as a driver, rather than a receiver, and it's unity-gain, so I'd still need to restore the output levels. Also the data/clock nature of my signal means that I have to be careful about skew between the two signals. That's basically why I started looking at LVDS receivers... with appropriate biasing, and using e.g. a quad device with an external termination resistor, they're low-skew and relatively tolerant of the absolute amplitude of signal swing.

Steve

Why - LVDS are cheap and readily available ?

The only other option is some high speed comparator ?

Some LVDS devices have a watchdog system in them, so idle -> known state, so beware of that.

Often the Common mode range is good on LVDS.

-jg

This one, for example : DS90LV028 has good CMR, and should suit 80Mbd well. Dual Channel, in SO8, or smaller.

-jg

Yes, that's pretty much my thoughts too.

Yes, noted. I'm biasing anyway to use it in single-ended mode.

Heh - almost exactly the part I had in mind ;). I'm actually using its sibling, the DS90LV048, simply because a) I've just used it in another design and b) it's available from stock from Farnell and RS here in the UK.

Steve