Sync wirelength

[m27]

In my setup the distance between my two optihubs is longer than 5 metres, then the supplid wire is not ling enough. Can we subitute it for any coaxial wire?

Thank you

[VincentG]

The RCA cable is not restricted to 5 meters (15+feet). We currently sell a 30ft. RCA cable for syncing.

[rschoele]

Hi,

I have a follow up question on Sync wire length. I'd like to use the optihub's external sync line to drive a custom device. Are the TTL electrical specs on the output linear to what is on the sync input? If the optihub's sync input is being generated internally or via a software trigger what is the external sync output voltage levels? Is it LVTTL with Vih of 3.3V?

Thanks
Ryan

[wing]

The spec of the output-driver for the External Sync Output is here (Vcc=3.3V):
http://focus.ti.com/lit/ds/symlink/sn74lvc2g34.pdf

The spec for the External Sync Input is: Vil(max)= 0.8V, Vih(min) = 2.0V

[rschoele]

nice -thanks
Ryan

[rschoele]

hi,

Another question regarding this. So I got that data sheet for the buffer gate from you and I called your tech support line and found out that the cable that connects to the External SYNC Out should be a 50ohm coax. Looking at the data sheet of the buffer gate it doesn't put out enough current to drive 50ohms.

What is the source termination of the optihub's External SYNC Out?

Thanks
Ryan

[wing]

"Doesn't put out enough current..." ?? Refer to Pg2 of datasheet. The buffer can sink/source 24mA at Vcc=3V. For a Voh of 2.0V into a 50ohm load, Iout=4mA, well below the rated 24mA.


There is a 50ohm series termination resistor on Ext Sync Out.

[rschoele]

2V/50ohm = 4mA?

you mean 40mA?

Ryan

[rschoele]

with 50ohm in series, yes then its 20mA, which is below the rating.

[wing]

Correct, 20mA terminated into a matching 50-ohm load.

2V/(50+50)ohm.