UC3909 can not only detect the state of the battery and adjust the corresponding charging state, but also indicate the current charging state of the battery through the logic level. STAT0 and STAT1 are decoding pins UC3909 both charging states. their different combinations can form different charging states as shown in table 4.1. pin STATLV as high level output when in floating charge state. STAT 0 and STAT1 are output as open circuit collector, respectively, and a 10 K pull-up resistance is connected to the VLOGIC., respectively