CL8800: how RC bridge regulate the tap current?
It looks like the datasheet provides only this bit of help, in the "Overview" subsection of the "Design Information" section:


  Manually selecting values will provide light, but the chosen values
  may be far from optimal in regards to efficiency, LED utilization, and
  line regulation. Contact your nearest Microchip Field Applications
  Engineer for design assistance.


It doesn't look like this device is intended for the casual hobbyist.