LM2767 datasheet(8/21 Pages) TI

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LM2767

V+

CAP+

OUT

GND

Oscillator

Switch Array

Switch

Drivers

CAP-

LM2767

SNVS069D – FEBRUARY 2000 – REVISED AUGUST 2015

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8 Detailed Description

8.1 Overview

The LM2767 CMOS charge-pump voltage converter operates as a voltage doubler for an input voltage in the

range of 1.8 V to 5.5 V. Two low-cost capacitors and a diode (needed during start-up) are used in this circuit.

8.2 Functional Block Diagram

8.3 Feature Description

The LM2767 contains four large CMOS switches which are switched in a sequence to double the input supply

voltage. Energy transfer and storage are provided by external capacitors. Figure 11 illustrates the voltage

conversion scheme. When S2 and S4 are closed, C1 charges to the supply voltage V+. During this time interval,

switches S1 and S3 are open. In the next time interval, S2 and S4 are open; at the same time, S1 and S3 are

closed, the sum of the input voltage V+ and the voltage across C1 gives the 2V+ output voltage when there is no

load. The output voltage drop when a load is added is determined by the parasitic resistance (Rds(on) of the

MOSFET switches and the ESR of the capacitors) and the charge transfer loss between capacitors. Details are

discussed in Application and Implementation.

8.4 Device Functional Modes

The LM2767 is always enabled when power is applied to the V+ pin (1.8 V

≤ VIN ≤ 5.5 V). To disable the part,

power must be removed.

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LM2767 Datasheet(PDF) 8 Page - Texas Instruments