We have a removable LiPo battery that we're trying to charge with the BQ24050. The BQ24050 is always powered via USB and we switch in batteries as they need to be charged.
The battery packs have 3 pogo pins. The GND pin is longer so it makes contact first. The VDD and TS pins are shorter and should make a connection at roughly the same time.
Right now, the TS pin on the BQ24050 is left floating.
The issue we're seeing is that the CHG_L pin is not turning on when a battery is inserted. We've diagnosed that if we make the TS pin on the battery *before* the VDD pin, the CHG_L pin works properly. It goes low on battery insertion and turns off after the charging cycle ends.
Is there a pin connection sequence that must be made for the CHG_L pin to work properly? Does GND and TS need to be connected before VDD is connected? If so, what is the relationship/timing between these connections that are required?
For TTDM, I can't say I fully understand this. It sounds like it's a way to charge a battery that doesn't have a temp sensor and the charger will just apply a constant current until 4.2V is reached. We don't need this capacity as our batteries will always have a 10k sensor on it. In the datasheet is the following note for TS:
"Floating TS Pin or pulling High puts part in TTDM and disable TS monitoring, Timers and Termination. Pulling pin Low disables the IC (CE function). If NTC sensing is not needed, connect this pin to VSS through an external ‘50/55-10-kΩ /’52-100-kΩ resistor. "
So, floating or pulling high disables TS sensing, which isn't what we want. But pulling low disables the charger altogether? What is the proper pullup/pulldown config to enable the TS sensor?
Thanks,
Alex
