regarding opto isolators

[prav]

Hi all,

I was studying some board schematics. In this there are some clocks
coming from external world . Before these clocks are connected to the
FPGA pins they pass through an opto isolator.Could any body help me
out why the opto isolators are really required .

rgds,
prav

 

[Vladislav Vasilenko]

prav wrote:

Hi all,

I was studying some board schematics. In this there are some clocks
coming from external world . Before these clocks are connected to the
FPGA pins they pass through an opto isolator.Could any body help me
out why the opto isolators are really required .

They usually required when the signal source has the
different ground potencial than FPGA has.
Often it occurs when the signal source is far from FPGA
and the signal and ground wires make a pair to prevent
noise errors.
In the medical installation it is the usual practice
because of voltage shield of patients.

But the opto isolator usually does not support
the high clokck frequency.

A.Ser.

 

[prav]

Hi Vladislav,

As u told that optoisolator dosen't support high clock frequency .
Are there any other alternatives to replace a opto isolator so that i
can work at higher frequency.

rgds,
prav

Vladislav Vasilenko <vlad@comsys.ntu-kpi.kiev.ua> wrote in message news:<402B57CA.9FD9FF73@comsys.ntu-kpi.kiev.ua>...

prav wrote:

Hi all,

I was studying some board schematics. In this there are some clocks
coming from external world . Before these clocks are connected to the
FPGA pins they pass through an opto isolator.Could any body help me
out why the opto isolators are really required .


They usually required when the signal source has the
different ground potencial than FPGA has.
Often it occurs when the signal source is far from FPGA
and the signal and ground wires make a pair to prevent
noise errors.
In the medical installation it is the usual practice
because of voltage shield of patients.

But the opto isolator usually does not support
the high clokck frequency.

A.Ser.

 

[glen herrmannsfeldt]

prav wrote:

As u told that optoisolator dosen't support high clock frequency .
Are there any other alternatives to replace a opto isolator so that i
can work at higher frequency.

Phototransistors are slower than photodiodes, and LEDs are slower
than laser diodes, though maybe fast enough. You might try a separate
laser diode photodiode pair.

-- glen

 

[Eric Smith]

praveenkn123@yahoo.com (prav) writes:

Are there any other alternatives to replace a opto isolator so that i
can work at higher frequency.

IsoLoop has isolators that run up to 35 Mbps.

http://www.nve.com/products/isolators/isproducts.php

 

[Antti Lukats]

"prav" <praveenkn123@yahoo.com> wrote in message
news:863df22b.0402122322.77eac1ee@posting.google.com...

Hi Vladislav,

As u told that optoisolator dosen't support high clock frequency .
Are there any other alternatives to replace a opto isolator so that i
can work at higher frequency.

www.analog.com

optical isolation for data rates 100M

antti
www.openchip.org