Hello
With my last problem regarding simple switchers being solved I'm now facing a new one.
After reading the datasheet several times I decided to try out the LM2623 in an application where the voltage input is limited to 2.5V and where the output preferrably would reach 12V at a 100mA load.
I did numerous tries to get correct C3 value with the suggested method in the datasheet, trial and error that is, without any luck. Only conclusion I could get was that with low value C3 (3.3pF -> 4.7pF) the current drawn by the circuit sky-rocketed to ~2A. And with higher value C3 (10pF > 33pF) there was less current drawn but no way near 12V out, closer to 7-8V. All tests were done with voltage divider calculated according to datasheet, 82k resistor for switch frequency and with a 4.7uH/3.2A inductor.
My question is if it's even possible to get 12V out from the LM2623 with the said input and if so, any pointers in how to choose the correct C3? Also I can see that the datasheet states output as high as 14V but I have no idea if it can deliver that from such a low input as 2.5V.
Best regards
Andreas