vout <= vin when gate <=1 and vref < vout,
when gate <=0 and vref > vout,
when gate <=1 and vref > vout
vout <= 'z' when gate <= '0' and vref < vout
Seeming a simple gate structure with a controlling of the output signal, perhaps for fan out check. On the other hand depending on the load and the on-resistances of the mosfets this could be an ocillator circuit.