Cxlb7218a is a charger circuit that can charge single lithium ion or lithium polymer rechargeable battery at constant current / current / voltage. The inner part of the device includes a power transistor, and no external current detection resistor and resistance diode are needed for application. Cxlb7218a only needs a few peripheral components and conforms to the USB bus technical specifications, which is very suitable for portable applications. The thermal modulation circuit can control the chip temperature in a safe range when the power consumption of the device is large or the ambient temperature is high. The output voltage is 4.2V and the accuracy is 1%. The charging current can be adjusted by an external resistance. When the input voltage (AC adapter or USB power supply) is powered off, the cxlb7218a will automatically enter the sleep mode of low power consumption, and the current consumption of the battery is less than microamps. Other functions include low input voltage detection, automatic recharging, chip enable input, battery temperature monitoring and status indication