Sorry to trouble you. We now use AD8351 just as below shows, Vocm tie to GND through 0.1uF capacitor.
The normal value of Vocm=1.65v as Vcc is 3.3v. But when input pulse signal(have risk coupling low interfering signal), sometimes the Vocm not equals to 1.65v, can you kindly help to advice what's the problem? Thank you.