The log amp detector in ADL5386 can be used to implement an AGC(Automatic Gain Control) loop. A portion of the output signal of the VVA is coupled to the input of the log amp detector. The output current from log detector is compared with the current from VSET. And any net difference at current between these two controls VVA and realizes AGC. So arrow (red circled below) should go out from log detector block. It will be corrected at datasheet revision.