Hi Srinivasa,
I would say; apply pls a reference voltage of ca 2.5V at pin 3, but with some good bypassing as 100nF X7R type and an AC coupled input signal.
Is your sine wave signal GND symmetric?
If you say: "I am measuring the LVDS signals(each) with respect to GND. for 1Mhz output is 0 to 3.3V square wave." > you means on LVDS31/pins 2&3?
I think its inpossible_as said Frank & Keith too!
LVDS is per default/standard a signal/pulse between 1,1...1,3V (around hes threshold of 1.24V)...
Maybe is some wrong at Power & G/Gb pins
As said too: check pls first the comparator output alone (separate from LVDS31) for your 30MHz!
I think, that your comparator works not in reality_so far Uref at 0.25V is-can not. It needs a threshold what in accordance of input signal rail is.
As said, in my opinion is better to use Uref at 2.5V& AC coupled input_than is the distortion of duty cycle smaller too as in these situation
...
Good progress!
K.