The AD8131 SPICE Macro-model Revision 2.0 (08/10/2012) Developed by JG/ADI downloaded from ADI website
does not work as expected when driving Vocm pin with an external common mode voltage greater than 2.7V.
According to AD8131 DataSheet rev G (page 5 Table 2) we expect that -Vs=-5V < -3.6 V < Vocm < +3.6V < +Vs=5V
But due to the Spice model bloc "VOCM INPUT RAIL CLIPING" the Vocm input is clamped to 2.88V +- VDX
therefore when Vocm rises over 2.7V, the output common mode voltage of the AD8131 saturate to 2,93V
and the AD8131 sink too much current at Vocm input
See attached Tina simulation schematic with various settings of Vcom input,
showing excess currrent sink on AD8131 input when voltage rise over the input clamp.