To summarize, C1 is a 1 µF ceramic at a voltage rating 10% greater than VIN Max. This must be an X7R not aY5V ADJ can be left floating but if the user wants to increase noise immunity on the pin add a 10 nF ceramic capacitor. C3 reduces ripple current in the LED. Without it the LED is subject to peak currents of +/-15% of the average current. Adding a 1 µF X7R rated at the VIN voltage will reduce this to under about a factor of 3. This has no effect on efficiency or frequency but does increase start up delay.

