I tried to use ADP3331 to get a low noise 4V power supply. Whatever I do I can't get a stable output. I used 392k and 909k resistors as a voltage divider and sometimes I managed to get stable 4.2V (in two different PCBs), but usually I get a very low output voltage (like 1.5-2.0V) that rises very very slowly (over a minute) and sometimes reaches 4V, sometimes something like 3.6V.
I tried to put different capacitors (1u, 10u, etc.) with different dielectrics (X5R, X7R, tantalum) very close to the input and output pins, but that didn't help. Input voltage is 6.0-6.5V.
I never had such strange problems with other regulators (although I used only fixed-voltage low-dropout ones and adjustable non-low-dropout).
Do you have any suggestions?