LM2665 CMOS charge pump voltage converter acts as a voltage doubler with input voltage in the range of 2.5V to 5.5V. Two low-cost capacitors and a diode are used in this circuit (required during startup) to provide an output current of up to 40 mA. The LM2665 can also be used as a voltage divider, splitting the voltage between 1.8V and 11V in two.
Test Circuit
The LM2665 operates at 160 khz oscillator frequency to reduce output resistance and voltage ripple. The LM2665 operates at only 650 μA (over 90% efficiency for most loads) with a typical shutdown current of 1 μA, providing ideal performance for battery-powered systems.
Functional Block Diagram
The LM2665 contains four large CMOS switches, switched in sequence to double the input power supply voltage. The transmission and storage of energy is provided by external capacitors. Figure 10 illustrates the voltage conversion scheme. When S2 and S4 are off, C1 charges to the supply voltage V+. During this period, switches S1 and S3 are open. For the next interval, S2 and S4 are open; When S1 and S3 are closed, the sum of the input voltage V+ and the voltage at both ends of C1 is 2-V+ output voltage. The output voltage drop at increased load is determined by the parasitic resistance (RDS(on) of the MOSFET switch and ESR of the capacitor) and the loss of charge transfer between the capacitor.
Voltage Doubling Principle
