18650 lithium battery charger based on IP5303/IP5305

Following the IP2312 charger, the 18650 lithium battery charger is produced based on Yingjixin IP5303/IP5305.
IP5303/IP5305 is a mobile power chip. This project only uses its buck charging function and does not use its boost discharge function. 1.2A synchronous step-down charging, efficiency 93%; input overvoltage and overcharge protection.
Rated input voltage: DC5V.
Applicable battery: 4.2V 18650 battery.
The charger is equipped with a battery reverse connection protection circuit. The battery reverse connection LED2 lights up, indicating a battery reverse connection error:
LED indication:
Status
LED
Charging
error
USB is powered on but the battery is not connected. Flashes off. Battery reverse connection
is
off . Charging flashes off . Fully lit. Off. Advantages : (1) Compared with the linear step-down TP4056, the IP5303/IP5305 integrated synchronous switch step-down charging efficiency is higher and the heat generation is lower. (2) Compared with IP2312, IP5303/IP5305 has fewer peripheral components; tested using the same old battery, it can turn the light when fully charged. Disadvantage: Both the power-on and charging indicator LED1 flash, and it is impossible to distinguish whether the battery is connected or not. Welding precautions (1) After USB type C is soldered, use a multimeter to check the adjacent pins using the on and off settings to confirm there is no short circuit. (2) The LED light-emitting surface faces the PCB for welding