LM828

Switched Capacitor Voltage Converter

General Description

The LM828 CMOS charge-pump voltage converter inverts a

positive voltage in the range of +1.8V to +5.5V to the corre-

sponding negative voltage of −1.8V to −5.5V. The LM828

uses two low cost capacitors to provide up to 25 mA of out-

put current.

The LM828 operates at 12 kHz switching frequency to re-

duce output resistance and voltage ripple. With an operating

current of only 40 µA (operating efficiency greater than 96%

with most loads), the LM828 provides ideal performance for

battery powered systems. The device is in a tiny SOT-23-5

package.

Features

n Inverts Input Supply Voltage

n SOT-23-5 Package

n 20

Ω Typical Output Impedance

n 97% Typical Conversion Efficiency at 5 mA

Applications

n Cellular Phones

n Pagers

n PDAs

n Operational Amplifier Power Supplies

n Interface Power Supplies

n Handheld Instruments

Basic Application Circuits

Voltage Inverter

DS100137-1

+5V to −10V Converter

DS100137-2

March 1999

© 1999 National Semiconductor Corporation

DS100137

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