The device is composed by a comparator LTC1541 where the analog control input voltage is applied. In the SPICE simulation the input is a piece wise linear voltage. The second IC, the LT3796, implements a boost driver with input current monitor that adjusts the DC current in the leds string. In this configuration the input to LT3796 can vary from 8 to 20 volts, the output is 35V, 1Ampere. The switch frequency is 400khz.