The charge pump uses an external fast charging capacitor (Flying Capacitor) to switch internally at a certain frequency to charge the capacitor, and to perform step-up (or step-down) conversion together with the input voltage. Finally, output at constant voltage.
There is a negative feedback circuit inside the chip to ensure the stability of the output voltage. As shown in the figure above, Vout is divided by R1 and R2 to obtain the voltage V2, which is compared with the reference voltage VREF, and the error amplifier A is used to control the charging time and charging of the charging capacitor. Voltage to reach a stable value.
The charge pump can continuously change its output voltage according to the battery voltage input. For example, it can run in either 1.5X or 1X mode. When the battery's input voltage is low, the charge pump can generate an output voltage equivalent to 1.5 times the input voltage. When the battery voltage is high, the charge pump operates in 1X mode, and the load charge pump just transmits the input voltage to the load. This reduces the input current and power loss when the input voltage is high.