[time-nuts] Sine to LVDS

Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Sep 9 11:07:56 UTC 2011

Javier Herrero wrote:
> Hello all,
> I think that the same question that has been discuted here a zillion 
> times but usually around 10MHz... anyway, what would be the best way 
> to convert a sine wave to a LVDS clock (preferably duty cycle 50%) at 
> 180MHz?
> Texas Instruments suggest a LVDS receiver as a comparator 
> http://www.ti.com/lit/an/slyt180/slyt180.pdf but time ago this was 
> discussed here, and not very favoured due to the high hysteresis of 
> the LVDS receivers.
> Regards,
> Javier
Use a true LVDS comparator (e.g. ADCMP604).
With 1:1 transformer coupled input and a pair of inverse parallel 
schottky diodes across the inputs together with series resistors between 
the transformer secondary to the comparator inputs should suffice for 
inputs of +16dBm or more.
With sufficient input from a low noise source a cycle to cycle jitter of 
1-2ps should be feasible.

Sub picosecond jitter is feasible if one cascades a series of low pass 
filtered limiter stages.


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