Other Parts Discussed in Thread: BQ25504
I've tried to remove all capacitors one by one (C5, C7 and C32), didn't work either.
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I'll verify those questions today and get back with answers asap.
Thanks,
Caio
Gautham said:
We will need to make sure the harvester is able to provide beyond the Iq consumed by the TPS. it has around 50uA of quiescent current. Also I am not sure the behavior of the TPS under the UVLO voltage.
Why does it work sometimes (at least once)? Actually, the problem is not really about the TPS behavior under voltage, I really want to understand is why the BQ can't output the expected voltage with a fully charged battery connected.
Gautham said:
Having a switch is truly isolating the output of the BQ and the input of the TPS. Is it possible for you to use the VBAT_OK signal to drive a load switch or the EN pin of the TPS?
We could take out the capacitor C11 (that is grounding both VINA and EN) and connect to VBAT_OK, but according to the TPS datasheet, I believe this capacitor is necessary for VINA.
Thanks for the answers,
Caio
We managed to put a transistor between BQ and the load/TPS, driven by VBAT_OK, removing the mechanical switch. The schematic now is as follow:
The system still behaves weirdly.
With the solar panel obscured, we plug in the battery and the system started fine, but then we removed the battery and plugged it in again - no good. VBAT_OK was 0 and BQ output hovers around 450mV, slowly going down to around 65mV. If we somehow "discharge" the BQ output (either shorting it or waiting for it to slowly discharge) before plugging back in the battery, the systems works fine.
What might be happening? Is this expected? If yes, what am I missing?