I have two different boards designed for the ADP2108. After assembly, both boards seemed to be stuck at 1.0V output. The input voltage is supplied by 5V USB (measures 4.8V) with 1.0A output capability. With 2xAA batteries connected (roughly 3.2V), I would expect to see the ADP2108 pass this voltage through to the output. But no, it sticks at 1.0V.
I assembled 2 new boards with just the power supply components and load tested with a potentiometer on the output. What I discovered is that the devices will produce 3.3V until about 200mA. Anything more and the output drops suddenly (not progressively) to 1.0V. THe only way to restore 3.3V output is to cycle the input power with the load removed.
As one of my fault finding steps, I ordered and used the exact 1.0uH inductor and 10uF capacitor recommended for the ADP2108. No change in performance.
I've attached scope traces from the one board - hopefully this will shed some light on the problem.
ADP2108 SW Signal at 100mA load. Output Voltage 3.3V
ADP2108-3.3 Switch Signal at just over 200mA. Output drops to 1.0V
Here's the board
Any ideas on what could be wrong here?