SN65LVDS104: fan out buffer 148.5MHz clock

Hi Leslie,

The LVDS104 should be compatible with your clock source.  If the Si591's output signal is DC-coupled and terminated with 50-Ohm pull-ups to +1.8 V, it should produce a .7- to 1.2-V differential signal at a common mode of +1.05 V.  These numbers come from the Si591 datasheet's CLK+/- Output Levels and Symmetry Table.  The LVDS104 requires input voltages on the bus pins between 0 and +2.5 V, and can detect differential signals of at least +/- 100 mV.  I see no problem with interfacing the two devices.

If you decide you want to AC-couple, I have attached a TI app note that details how a CML source can be interfaced with an LVDS receiver such as the LVDS104.  Basically, it recommends that the CML signal is terminated to Vcc on the source side, then AC-coupled and re-biased to an LVDS common mode at the receiver.  Again, in this case AC-coupling is not a requirement.

As far as alternate sources, I am not sure.  There are many available options when it comes to oscillators.  There may not be a direct replacement for the Si591, but looking around on a few vendor websites turned up a good amount of devices that could output a 148.5 MHz clock.  Also, the Si591 can be purchased as a 3.3-V LVDS output device, which may simplify the design.

Please let me know if you have any additional questions.

 Best regards,

Max

Sorry!  Forgot to attach the app note.

- Max