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Some configuration questions-Connecting ADP5090 to Piezo Harvester

Question asked by nr1engineer on Jan 23, 2016
Latest reply on Feb 2, 2016 by nr1engineer

Hi everybody,


im working currently on a project and have some configuration problems with it. There are some piezoelectrical harvesters connected through rectifier to the capacitor Cin. The energy stored there should be transfered to the solid state battery connected to BAT pin of ADP5090. This energy is extremly small so i have put a low power FET switch between Cin and Vin pin, that will be turned on for 30 seconds every 15 minutes to enable energy transfer. The purpose of this curcuit is just to charge the battery, so i dont need SYS pin for the other circuit because it is connected directly to the battery and consumpts just few nanoamps.

I will be very thankful if you can answer the following questions:


1)To avoid any useless current consumption i have disabled MINOP(connected to GND) and MPPT(left float) functions. The datasheet has some contradictory information. What should i do with CBP pin??? Should i connect it to Vref pin as the Table 4 says or should I connect MPPT and CBP to GND like if that was an ideal voltage source(Chapter - Vin open circuit and MPPT)???


2)As i have already said, i need just the charging process of the battery, so the SYS pin is not used. The battery will be already charged by plugging in. Does that mean the converter wont need cold start up? Do i need the capacitor on SYS pin then? Anyway, the SYS function consumpts >250nA. How can I avoid it? It takes 260nA from my battery when Vin is 0V. And it still takes 320nA when Vin>0V while charging. What will happen when i will connect SYS pin to GND while Vin is 0V? It will consumpt only 0.5 nA right? And how can i charge the battery then? Should I disconnect SYS from GND and connect it to the battery or just leave it floating?


3)What is with the DIS_SW pin? Can it be left floating when not used or be connected to GND for constant switching enable?


4)How can i disable PGOOD function? Is it okay wheh i leave SETPG pin and PGOOD pin floating?