Hello,
We are evaluating the BQ27621 for replacing a competitor's product in our application. We have a device powered by external dumb battery packs that can be hot-swapped, and use the fuel gauge for indicating "pack low" condition. Packs are recharged separately by a standalone charger. Our accuracy requirements are modest and the flexibility of using various sizes of dumb external pack without additional characterization makes the BQ27621 an attractive choice.
It is possible, however, for a determined user to connect the external pack backwards (positive and negative terminals swapped). It is not easy, but Murphy's Law applies and sooner or later someone will do it. The system is fully protected against reverse voltage, but because the fuel gauge is so close to the battery, it sits before our protection. The BQ27621 datasheet suggests that this condition would be problematic, exceeding the absolute maximum ratings, but provides no direct guidance. That is also the case of the competitor's product we would like to replace, but our in-house testing shows that that part can tolerate the reverse voltage without a noticeable change in function or accuracy.
(For what it's worth, we do not have a clean analog supply rail greater than the battery voltage available in this area of the design.)
Are there recommendations for how to handle this situation with a BQ27621? We've ordered the EVM and can do some basic testing but any direct feedback or test results from TI would be useful.
