Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Differential line receiver

Status
Not open for further replies.

hithesh123

Full Member level 6
Joined
Nov 21, 2009
Messages
324
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,298
Location
lax
Activity points
3,548
I am looking for differential line receiver 0 -30V or close to that range.
I found a driver - OL7272. It seems to be a default standard.
But I cannot find the receiver equivalent of the chip.
 

dick_freebird

Advanced Member level 5
Joined
Mar 4, 2008
Messages
6,915
Helped
2,025
Reputation
4,054
Reaction score
1,865
Trophy points
1,393
Location
USA
Activity points
55,373
That's a crazy high swing for a transmission line. Used to
be some aircraft (1553?) busses that had that kind of a
transmitter swing, transformer coupled. Not sure if the
full amplitude was presented to the receiver, I only had
occasion to touch the transmitter long, long ago.

If you can't find a purpose designed receiver chip, a
generic comparator with a large differential input signal
range might do as well. Probably just missing some
fault response modes (you could use additional comps
for that if you cared).

In RS-232, RS-485, RS-422 designs an input attenuator
network is the norm, pulling the signal range from (say)
+/-7V at the pins to 1-2V at the internal comparator
using isolated resistors. You trade signal range for some
speed, power and have to watch the offset voltage and
low-overdrive switching performance.
 

hithesh123

Full Member level 6
Joined
Nov 21, 2009
Messages
324
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,298
Location
lax
Activity points
3,548
The 7272 are used to drive signals from encoders (shaft encoders). 30V is high. I don't think it can go upto 4MHZ at 30V swing.
I was looking at 26LS32 and other diff rcr datasheets. Most of them say the positive threshold is 200mv and -ve threshold is -200mV.
When they say -ve threshold do they mean it with respect to ground or the mid point of differential input signals?

The datasheet of DS96173 shows an input signal (VID) swinging from +2.5 to -2.5v.
I dont understand. Vcc is 5V, but VID is -2.5V?
http://images.elektroda.net/34_1306957070.jpg

How far apart should my input signals be to get an output?
Assuming the thresholds level are with respect to mid point of diff signals, I concluded VID of 400mV should be good enough.
One input oscillates between 0 to 200mv and the other from 200mv to 400mv.
Am I correct?
 

dick_freebird

Advanced Member level 5
Joined
Mar 4, 2008
Messages
6,915
Helped
2,025
Reputation
4,054
Reaction score
1,865
Trophy points
1,393
Location
USA
Activity points
55,373
VID is -differential- voltage, which has to be developed
subject to the VCM common mode range (or a pair of
individual pin absolute ranges, depending on the spec).

In your 5V case -2.5V VID could be (say) VINP=1.25V
and VINM=3.75V while +2.5 VID would be VINP=3.75V
and VINM, 1.25V. Neither pin exceeds the rails although
some line receivers support that.
 

hithesh123

Full Member level 6
Joined
Nov 21, 2009
Messages
324
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,298
Location
lax
Activity points
3,548
VID is -differential- voltage, which has to be developed
subject to the VCM common mode range (or a pair of
individual pin absolute ranges, depending on the spec).

In your 5V case -2.5V VID could be (say) VINP=1.25V
and VINM=3.75V while +2.5 VID would be VINP=3.75V
and VINM, 1.25V. Neither pin exceeds the rails although
some line receivers support that.
Yup, you are right. I realized after I saw the differential signals.
They are just signals with 180 deg phase difference.
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top