[time-nuts] IC for 1 PPS Output

Bill Janssen billj at ieee.org
Fri Apr 7 11:31:20 EDT 2006

Brooke Clarke wrote:

>I've got the TVB 1 PPS PIC circuit working and would like to add an 
>output IC to drive 50 a couple of Ohm cables.
>Need two outputs, the normal 1 PPS and also the 10 kHz output since I 
>think it would work with the SRS app note for making 1,000 TI 
>measurements in one second to better see small offsets.
>I seem to remember that there may be an internal resistance already in 
>some chips so putting a 47 or 50 Ohm resistor in series may result in an 
>impedance above 50 Ohms.  Any thoughts?
>Brooke Clarke
Why do you need to drive the cable with a 50  Ohm source. You need a 50 
Ohm load on the receiving
end to reduce reflections. But that is not a problem for the drivers. I 
would use a low impedance
driver to minimize losses in the driver.

Just my approach.
Bill K7NOM

More information about the time-nuts mailing list