Tool/software:
Hello,
I have an issue with the behavior of the BQ25157 in certain specific cases.
The system in which the BQ is embedded is standalone, with a battery powering the system — there is no external source other than the charger.
The battery used has an operating range from 3.2 V to 4.2 V.
The BATUVLO setting range only goes up to 3.0 V, so I disable this functionality (Register 0x16 bits [2–0] = 0b111).
My charger is quite low-power and its voltage varies, so I need to disable VINDPM (Register 0x18 bit 7 = 1b1).
These settings are volatile and therefore lost when I enter ship mode.
When the battery is at 3.3 V, I put the BQ25157 into ship mode to preserve battery life. If the battery remains on the shelf for a long time, it may discharge down to 3.0 V.
It’s when the battery drops below 3.2 V that I observe strange behavior:
1. If VBAT > 3.2 V, PMID is enabled when VIN > VBAT + VSLP → OK, charging works normally.
2. If VBAT < 3.2 V, PMID is enabled only when VIN > 4.2 V → OK, charging works, but why is there a 4.2 V VIN threshold now?
3. If VBAT < 3.2 V and VIN remains below 4.2 V, no charging occurs. If the charger is removed, PMID is NOT enabled, the always-on 1.8 V LDO stays active, and around 400 µA are drawn from the battey.
It there a solution to return into ship mode automatically if the charger failled to reach 4.2V I am afraid to kill the battery if 400µA are drown on a already discharged battery.
Please tell me if this behaviour seems normal for you?
Thank you for your help.
