if I start it with low load (100mA or less), it starts normally and I can increase load at this point up to 280mA(or may be higher) and it will keep stable and clean 3.3V
if I start it with load 200mA or higher, it never goes above battery voltage (2.1-2.4V) and if I keep it for few seconds kills chip permanently.
Schematics as shown in the datasheet (see attached), except:
- input capacitor is 22uF ceramic
- LDO is not used and not connected
- LBI is not connected
I've no idea why it's having the problem you described.
On the datasheet it looks like it takes a while for the converter Vo to reach it's target voltage. So just let it start up before you draw current. There's a PGOOD output that goes high when Vo is where it should be; try using this output to enable your load.
In this specific application I should not have any problems to sequence load: I can start PIC18F first, and it can turn LCD backlight and Ethernet module once PGOOD is set.
But I would like to have this design for future appliactions where I may need to have 200mA load on power up.