We are using the BQ27421-G1 in our design and have been experiencing an issue where the chip seems to be entering SHUTDOWN mode without being instructed to do so by our MCU. Our system detects this condition after it is no longer able to communicate to the BQ27421 via the I2C bus.
At first we thought there was an issue with the I2C bus and found the following support ticket here that describes a workaround to reset the bus communications of the BQ27421 by pulling the SCL and SDA lines low for 2 seconds, but this did not restore the communications.
In the E2E forum, we were able to find someone that is experiencing the same issue here, but it was taken "offline". Why, I'm not sure. That seems to go against the usefulness of a forum.
We measured the VDD pin (1.8 V LDO output) and confirmed that the output was ~0V, meaning the BQ27421 was in SHUTDOWN mode. As per the Technical Guide, toggling GPOUT high for 200 us will force the BQ27421 to exit shutdown. Since we missed the note recommending that this line be attached to an MCU pin, we had to force this manually with just a wire. After doing so, the communications to the BQ27421 was revived.
With respect to our layout, we have reviewed our design and *believe* have done everything correctly. Of course, we could have missed something.
Is anyone aware of the conditions that may cause the BQ27421 to enter SHUTDOWN mode? Can anyone offer any more insight?
We have three products that use this device and the team is leaning towards immediately replacing the device if we can't find a reliable solution.
