PCB effect drawing, scheme description (making method)(1) main charging chip selection. TP4056 is a complete single lithium-ion battery linear charger with constant current and constant voltage. SOP8 / MSOP8 packages with fins at the bottom and fewer external components make TP4056 an ideal choice for portable applications. TP4056 can be used for USB power supply and adapter power supply. Because of the internal PMOSFET structure and the anti-reverse charging circuit, there is no need for the external isolation diode. Thermal feedback automatically adjusts the charging current to limit chip temperature under high power operation or high ambient temperature conditions. The charging voltage is fixed at 4.2 v and the charging current can be externally set through a resistor. TP4056 will automatically terminate the charging cycle when the charging current reaches 1 / 10 of the set value after reaching the final floating charging voltage. When the input voltage (AC adapter or USB power) is removed, the TP4056 automatically enters a low current state, reducing the battery leakage current below 2uA. TP4056 can also be put in shutdown mode when power is available to reduce the supply current to 55uA. Other TP4056 features include battery temperature detection, undervoltage locking, automatic recharging and two LED status pins for indicating charging and termination. (2) the circuit design of the charging main chip. Circuit Design Reference Data Manual in the typical application of the circuit, as shown in the following figure: (3) regulator chip selection. Tlv700xx series low dropout (LDO) linear voltage regulator is designed for applications requiring high power consumption. The advantages of differential pressure and low output noise make the chip an ideal choice for battery applications. At the same time, the chip has switch control terminal and current limit. (4) the circuit design of voltage stabilizing chip. Circuit design reference data manual for typical application circuits, as shown in the following figure: (5) module testing. Plug the welded module into the USB port for power supply, you can see the red light is always on, the green light flashes, and then measure the battery output voltage, about 4.2 v on normal. Measurement of 3V3 Port Voltage, 3.3 v Regulator circuit is normal.