Anyone,
I am trying to connect a charger, BQ24105, and a gas gauge, BQ27500, via a common battery pack thermistor. I see a potential problem. The charger has to monitor the battery's temperature so that charging can be stopped if the temperature is outside an acceptable range. The voltage at pin TS calculated from the given equations should be between 1.084V and 2.315V for charging to occur.
However, the acceptable voltage range on the TS pin of the gas gauge is between (Vss-0.125)V and 2V. Clearly, the translation of voltage to temperature is different for the gauge and the charger. This is strange to to me because if I were the designer, I would ensure that the translations are the same since there is typically 1 battery thermistor per battery pack.
I have the following questions:
1. How best to achieve an integrated system with BQ24105 and BQ27500. The simplest answer is to have 2 thermistors on the battery pack. Are there other ways?
2. What is the translation from voltage to temperature for BQ24105 and BQ27500?
3. It is mentioned that BQ27500 is pulled low when measuring battery pack temperature (pg 26 of 41 in BQ27500-V130 (aka SLUS914A)). What does low mean? Clearly it cannot be 0V. I believe it must be Vcc. But, nothing is stated about this anywhere.
Thanks for any and all relevant comments. Irrelevant comments should be funny at the minimal.
Jay