Anyone have any good reference material or app notes for Power over LVDS lines. I ran across this the other day. Google does not give me much. One usage seems to be powering rear view cameras in cars. I found a power point presentation from National Semi that had a couple of slides with a simple analysis of pushing 2A@12V on the diff pair.
-- Chisolm Republic of Texas
Isn't "12V LVDS" an oxymoron?
Link to the PowerPoint? ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
AC couple the data, dummy. Like PoE.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
There was also a mention about it in a Intersil presser for their ISL76321.
I would expect something a little more exotic than a Ethernet style POE given the signaling rates.
-- Chisolm Republic of Texas
Could be reasonable. Seems like it would be a variant of Power over Ethernet (PoE).
?-0)
Sounds like phantom feed for condenser microphones or Power over Ethernet. However, these use transformers to couple the signals.
To use transformers, the signal should not contain any data dependent DC offsets, so you would have to use Manchester coding etc.
Sorta. The schemes I've seen use capacitors at each end to couple the LVDS lines and inductors to isolate the DC. At the frequencies usually encountered, the parts are small and cheap.
I haven't seen transformers used for power over LVDS. Often there's only one LVDS line, so the common center-tapped PoE thing doesn't work.
The transmitters and receivers that support AC coupling are using
8b/10b Line Code to DC balance.I'll look through this and see if there is anything interesting
AC-Coupling Between Differential LVPECL, LVDS, HSTL,and CML
The Intersil part ISL76321 shows ac coupling in the data sheet with
27nf caps. This is for their 1G link but no power injection.When I have some time I'll sit down and work it out....
-- Chisolm Republic of Texas
isn't it +12 on the signal lines and ground return?
-- ?? 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
I'm not clear what the question is. The LVDS schemes I've seen are power on one and ground on the other, similar to the phantom microphone power scheme (above). I suppose you could put 12V on both and rely on another common ground for the return. Sounds like an EMI problem waiting to happen, though.
VDS
much.
ahe
xlr phantom power is gnd to gnd, ~48V via resistors to both signal wires
think you could use similar scheme for lvds, use inductors and caps to isolate power and signal so you can try to get proper differential termination
should few volts of common mode voltage to play with
-Lasse
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.