Part Number: BQ25505EVM-218
Dear Team,
I have a question regarding the behaviour of the BQ25505 when no energy harvester is attached. In order to close the switch between VSTOR and VBAT as I understood it, there are two conditions:
- The voltage of the battery attached should be higher then the undervoltage
- VSTOR should be discharged below 100 mV.
However, when testing with the evaluation board I run into the problem I need to discharge the BAT_SEC pin as well in order to reconnect the switch. I would like to ask anyone to explain to me why this is the case or how to overcome this. This is what I have done (Oscilloscope picture below):
Blue is the voltage over VSTOR pins, red is the voltage over the BAT_SEC pin
A: Connect the battery for a short while and then disconnecting it
B\C: Same as A. This behavior is expected.
D: Reconnecting the battery after the PFET has disconnected VSTOR and VBAT. It is expected plugging in the battery now does not reconnect the switch.
E: At this point I again reconnect the battery and I would expect the PFET to connect VSTOR and VBAT again, however this is not the case.
F: Only when I discharge the BAT_SEC pin, reconnecting the battery will reconnect the PFET.
I have tried this multiple times, always with the same result. Can someone please explain to me what is going on?
Regards,
Jan
