ZHCS688I November 2011 – March 2018 TPS65217
PRODUCTION DATA.
The TPS65217x device has a linear charger for Li+ batteries and a triple system-power path targeted at space-limited portable applications. The power path lets simultaneous and independent charging of the battery and powering of the system. This feature enables the system to run with a defective or absent battery pack and lets instant system turnon even with a totally discharged battery. The input power source for charging the battery and running the system can be either an AC adapter or a USB port. The power path prioritizes the AC input over the USB input, and both over the battery input, to decrease the number of charge and discharge cycles on the battery. Charging current is automatically decreased when the system load increases to the point where the AC or USB power supply reach the maximum allowable current. If the AC or USB power supply cannot provide enough current to the system, the battery supplies the additional current required and the battery will discharge until the system load is reduced. Figure 11 shows a block diagram of the power path. Figure 12 shows an example of the power path management function.
The detection thresholds for AC and USB inputs are a function of the battery voltage, and three basic use cases must be considered: shorted or absent battery, dead battery, and good battery.