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ADP5090-2-EVALZ very inefficient?

Question asked by NielsB on Nov 14, 2017
Latest reply on Nov 16, 2017 by Kevin.Yao

Dear reader,


For a school project we want to use the ADP5090-2-EVALZ as a power source for our Ultra Low Power project. The problem is that the kit doesn't seem to function as a high efficiency harvester. We measured the voltage at the BATT pin to get the capacitor voltage and used this to determine the amount of energy harvested in a given time. Below you see the charge characteristic, measured in the lab under a lightintensity of around 750 lux.

This seemed rather slow in our opinion, because this means only around 93 milliJoule (0.5*0.1*Voltage^2) of energy was stored in 2 hours. When we shortcircuit the solar panel to the BAT pin and the GND pin, the supercap was charged to 0.779 Volt in 180 seconds. So we guess that there is something wrong with the harvester, as this suggests a lot of lost energy in the harvester.


Our question is: Is this normal behaviour for this energy harvesting-IC, or is it simply broken? We have done a lot of measurements, so if you need more details we will be glad to share this data. 


Kind regards,


Bastiaan en Niels