Step-Down Charge Pump Regulator for USB Powered Devices


this is a circuit of Step-Down Charge Pump Regulator for USB Powered Devices. The critical design parameter of this circuit is the circuit area. To solve this problem we can use Charge pump step-down circuit. This circuit only requires   the charge pump controller and  four ceramic capacitors. So it is a low cost circuit because of the low cost of the ceramic capacitors. Here is the circuit :

Step Down Charge Pump Regulator for USB Powered Devices

The two flying capacitors are connected in various  parallel or series  configuration by internal FETs that is utilized by the controller. They will dump their energy to the output. The internal FET is automatically configured by the load and the input voltage. When the loads is greater than 150mA, controller will act as a LDO and stop using capacitor. the maximum limit of this circuit is 0.25 A, so this circuit only used for low power applications. For a light load, between 1mA to 50mA, the efficiency of this circiut is 80-90%. It will drop to 65% when working in LDO mode. [Source: Texas Instruments Application Note]


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