why cml to cmos converter needed

[manissri]

for refernce clk circuit my input is from 0 to 700mv for the supply of 1.2v
so for getting the cmos clk (from 0 to 1.2 volt)
why i need to put input pulsed into cml to cmos converter.
what benefit i can get. by using this one .
the other option is if i put this clk to an inverter i can get the full swing (0 to 1.2v)
clk.
so what is the diff by putting an inverter and cml to cmos con.

 

[ieropsaltic]

CML output swing is small and shifted by DC (common mode output of the CML stage). If this output is used directly to drive the CMOS standard circuits, it won't be sufficient to turn off the PDN and PUN networks present at the CMOS circuits, leading to large leakage and thus static power consumption and degrade noise margins .Also, CMOS are single ended input while CML is of differential output. CML to CMOS converter is single ended at output with differential input thus performs required conversion and rejects the input's common mode and can adjust its output common mode to achieve required swing to fully drive the CMOS stages.

 

[rowokii]

In addition what ieropsaltic states, another problem with driving 0-.7V clk signal into a inverter directly is your clock duty cycle will be badly distorted.