I am attempting to use the LTC3105 to regulate 5.25V. I am using 4 solar cells in parallel as the power source. At the max power point of the solar cells, they are rated at 1.67V and approximately 18.4 mA (so for four in parallel, that would be approximately 73.6mA). I set the mppc on the LTC3105 to 1.67V using a 167k resistor, however the output voltage does not reach 5.25V. Instead, it reaches approximately 2.5V. I have double checked my resistor divider that sets the voltage, and that looks ok, however I measured the FB pin and that was at 0.5V instead of the nominal 1.004V.
I tried lowering the mppc value to see what would happen, and I discovered that when I lowered the mppc to 1V, the output remained at 2.5V and the input remained at 1V (as one would expect). However when I flooded the solar cells with light the input voltage jumped from the programmed 1V input up to approximately 1.67V, which is the mpp of the solar cells. Once this jump occurred, I was able to achieve the regulated 5.25V output.
I don't want to have to flood the solar cells with light and break the mppc limit, as that is not how this part is supposed to work, so does anyone have a recommendation for how I can get this system to operate properly? Could the issue potentially be with the startup of the part? It seems like once I flood the system with energy it begins to work, but it does not work under "normal light" conditions. My input capacitance is 10uF - is this to low for an application such as this?
For reference, I have attached a pdf of the solar cells I am using.
Thank you very much,