LM2681

Switched Capacitor Voltage Converter

General Description

The LM2681 CMOS charge-pump voltage converter oper-

ates as a voltage doubler for an input voltage in the range of

+2.5V to +5.5V. Two low cost capacitors and a diode

(needed during start-up) is used in this circuit to provide up

to 20 mA of output current. The LM2681 can also work as a

voltage divider to split a voltage in the range of +1.8V to

+11V in half.

The LM2681 operates at 160 kHz oscillator frequency to re-

duce output resistance and voltage ripple. With an operating

current of only 550 µA (operating efficiency greater than 90%

with most loads) the LM2681 provides ideal performance for

battery powered systems. The device is in SOT-23-6 pack-

age.

Features

n Doubles or Splits Input Supply Voltage

n SOT23-6 Package

n 15

Ω Typical Output Impedance

n 90% Typical Conversion Efficiency at 20 mA

Applications

n Cellular Phones

n Pagers

n PDAs

n Operational Amplifier Power Suppliers

n Interface Power Suppliers

n Handheld Instruments

Basic Application Circuits

Voltage Doubler

DS100965-1

Splitting V

DS100965-2

March 1999

© 1999 National Semiconductor Corporation

DS100965

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