I am using ST1S03 in the inverting configuration shown in Design Note DN0011. Input 3.3 V +/- 7%. Output -3.3 V ~150 mA.
I am getting efficiency only ~69-72%. Which, now that I look into it, is not much worse than the datasheet typical value of 70-75% (for 5 V input, this configuration being equivalent to ~6.6 V input).
But it's not clear in the datasheet what assumptions were made in estimating or measuring the typical efficiency.
So, my questions are,
* How was the efficiency curve in the datasheet determined? What external circuit was used?
* I calculate only about about 0.056 W switch loss, ~0.02 W inductor loss, and ~0.03 W diode loss for my circuit. But total losses are about 250 mW. What are the other loss mechanisms I should consider?
* Can you recommend any way to improve the efficiency? (I'd like to get 75-80% if possible)
