Other Parts Discussed in Thread: BQ20Z45
I have an ongoing issue with the BQ20Z45 on two instances of my product. In both cases, it appears that an erroneous measurement of the TS1 external thermistor is causing a permanent failure. When logging in the BQEvaluation software, I see the TS1 temperature rise from 22 degrees C to 118 degrees C in a period of 4 seconds. It stays high, dropping to about 115 degrees C for about 15 minutes. Then, within 4 seconds, the temperature measurement drops right back down to 22 degrees. I just don't think it's possible for the temperature to decrease that sharply. The amount of mass (the thermistor is a chip type that is soldered to a PCB) that would need to cool for this to occur is considerable. In addition, there is a second thermistor on the board whose value does not move.
I am using the exact same thermistor circuit as is recommended in the datasheet. There is no doubt that a manufacturing issue could lead to this issue but I'm wondering if there are any known issues with the temp sensing firmware on any version of the BQ20Z45.
Thank you in advance!