What is that component from the ADP5091 Schematic?
From the block diagram and page 16


  The switching mode synchronous boost regulator, with an external
  inductor connected between the VIN and the SW pins, operates in pulse
  frequency modulation (PFM) mode, transferring energy stored in the
  input capacitor to the energy storage connected to the BAT pin. The
  MPPT control loop regulates the VIN voltage at the level sampled at
  the MPPT pin and stored at the capacitor through the CBP and the AGND
  pins. To maintain the high efficiency of the regulator across a wide
  input power range, the current sense circuitry employs an internal
  dither peak current limit to control the inductor current.




Also, 


  The boost regulator and regulated output in hysteresis boost mode in
  the ADP5091/ADP5092 includes current-limit protection circuitry to
  limit the amount of positive current flowing through the low-side
  boost switch