The last aspect of a battery charger architecture covered in this course is whether to use a standalone hardware solution or a software-controlled charger solution. For the standalone device such as the bq2407x series devices shown here, the implementation is relatively simple. Critical charge algorithm parameters such as the termination timer, peak system current limit, and peak battery charging current limit can be fixed by choosing the appropriate values for R1, R2, and R3. Additionally, there are simple logic hi/lo inputs that can enable the device and set different fixed current limit thresholds when charging from a USB source. Since these devices include internal power path FETs, the system can power up with a depleted battery whenever an external supply is connected.