I've calculated everything up and came up with the following.
Vin,max – 4.2v , Vfb = 0.1v , 1.8 <= Vf <= 2.4V, Vout – Vf + Vfb
fsw = 1.5MHz, 30mA <= I_led <= 250mA, I_led = Vfb / Rs
I set I_led to be 160mA and I_ripple is 40% of I_led ( 64mA). So, I got 10uH inductor. I guess I could get smaller inducter if I set I_led to be higher like 200mA or 250mA. Then, what would be the consideration. power dissipation?