Some questions :
1 ) What distance those boards are from that ?
2 ) What kind of cabling was used ?
3 ) That conducted signal was shielded ?
Please draw and post here where was placed the buffer ( close to IC ? close to connector ? )
+++
1.
How the boards share a ground is a typical problem in this situation.
Advice says you should connect the circuits as close as you can to a single ground point.
2.
There's a limit to how many devices you can fan out to. (Depending on the source device and the receiving devices.)
Did you try connecting one at a time to see when the original waveform gets distorted?
Hi
Distance of 1m is considerably far to distribute signals of that band magnitude at standard cablings.
However it´s possible to take a RF aproach to accomplish that transmission.
You could use an connector at board (BNC) despite it be very expensive.
For while I canno´t think in other cheaper option but surelly exists.
+++
20 MHz doesn't need RF approach...
I think it would be best to use individual driver devices to supply each cable. The lower the impedance the better. High impedances are susceptible to stray capacitance.
Also to make the cable pulses swing between zero and 5v. You can re-condition pulses to 2v-4v swing where it enters each board.
One meter cable distance. Lightspeed at 1 ft. per nanoSec. This means the 20 Mhz clock pulses may get slightly out of sync by a fraction of a cycle. Does this affect operation?
Some Scopemetters have exacly that 20MHz frequency specified in the Bandwidth.
And it probe cable is Coaxial type.
I may be wrong but due to some EM effects simple cablings could affect signal integrity rather than a self-shielded one.
+++
...Can you offer me some Parts or any reference ?
R37 and R38 connected to the buffer output don't seem to serve a reasonable purpose. They are mainly dissipating power. But you most likely would want a series termination for both clock outputs. Considering the buffer impedance, you'll come near to 50 ohm with a 43 to 47 ohm resistor. This would be at least the suggested driver impedance for a 50 ohm coax cable. A PCB trace may have a slightly higher characteristic impedance. I reviewed the thread, but didn't find substantial information about the properties of the connected "load", e.g. logic standard, input capacitance, only a 2-4V voltage level was mentioned.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?