Differential line receiver

[hithesh123]

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]

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]

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?
https://obrazki.elektroda.pl/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]

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]

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.