I have a switcher circuit based on LT3680. I implemented the typical circuit shown in the datasheet in a well laid out 4-layer PCB. However, I find that the input voltage is present at the output at no load condition. When I add load of 100ohms and below, I get 5.05 constant output. The typical circuit is meant for 5V, 3.5A load. My loads draw only a few milli amps. So could that be because if the inductor saturating or something. The switcher has feedback and as far as I understand should be able to regulate the output whatsoever. Regulation kicks in only when I add 100 ohm or below. Nothing with 10K, haven't tried with anything in between since I don't have a wide range of resistors available with me. Please have a look at the circuit used.
Datasheet can be found at: