Full order code = BQ27421YZFR-G1A
From the field, we get reports of battery problems: Battery detection, charge are not accessible.
Disconnecting the battery and reinserting the battery solves the problem. Even when this is not done, our products stays working, discharging, charging, …
It is not easy to reproduce this problem in the lab.
By analyzing the problem, we see that the fuel gauge does not respond to its I2C device address 0xAA. We see a NACK on the bus. (see image below)
The LDO voltage of the fuel gauge is not 1V8, but 0.5V. But when I measure a second time, it is 1V8 and everything works. Or I made a short during measuring, or the fuel gauge suddenly activates during measurement.
On the related post, 2 solutions were proposed:
- power cycle
- This solution works (removing battery and reconnecting battery), but we cannot ask this to our customers/users.
- toggle GPOUT
- In our schematic, GPOUT is only connected with a pull-up resistor to VDD.
Schematic:
As far as I know, we do not send I2C commands to put the fuel gauge into SHUTDOWN mode.
Questions:
- Do you know what is the root cause of this failure?
- With current hardware, what can we do to prevent this situation?
- Are there circumstances that due to … the fuel gauge automatically goes into SHUTDOWN mode?
- Can we disable to go in SHUTDOWN mode?
