Part Number: ATL431
Is there a shunt regulator (or other part) that will clamp to 3.6V the voltage from an indoor solar cell (say Amorton 1815 generating a few or tens of uA in dim light of say 200lux)?
In typical conditions, the solar cell V operating is low enough, but in stronger light the solar cell can generate a max voltage of say 5V (Voc open circuit of 8 cells@0.6V). That is higher than the Vmax the load (an mcu) can tolerate.I have looked at the TL431 but the "Imin Minimum cathode current for regulation" of 400uA leads me to believe it would not work. (But I have no experience with shunt regulators.)I have searched for a zener but can't find one that has an Ir low reverse leakage of less than a few uA and a sharp knee at Vz or Vr of 3.6V. I have evaluated a TVS diode (for ESD protection) but it didn't seem to clamp the voltage. Also, a TVS seems designed for a pulse, not for constant current (but I figured that the package could withstand the say 200uW from the solar cell.)I have tested the BQ25504 (which will clamp the Vbat output voltage) but I am looking for a simpler solution. (If I wanted to minimize the area of the solar cell, I would use the BQ25504. But most of the available amorphous solar panels for indoor light are already larger area and higher voltage than I need, not requiring the boost or MPPT of the BQ25504. Also, I am using a tantalum capacitor, not a super cap or battery which might require protection functions of the BQ25504.)My application is nano power, duty-cycled radios.
In reply to Diego Lewis: