ADL5391 Outputs single ended

Dear ADI Expert,

in my application the ADL5391 has to drive a single ended input from DC to a few MHz. For symmetry both outputs WP and WM of ADL5391 are connected by 200 Ohms to GND (COMM). Surprisingly to me the outputs do not swing symmetrically around the common voltage VPOS − 2.5 (i.e. 2.5V in my case), but around 1.8V.

In the same application a second ADL5391 drives the inputs XP and XM of another ADL5391 differentially, but the mean output voltage (WP+WN)/2 is 2.25V, not 2.5V.

How do the outputs swing single ended?? Is it somehow related to the common mode voltage of any input?

Kind regards,

Dipl.-Ing. Sven Probst.