LM2687

Low Noise Regulated Switched Capacitor Voltage

Inverter

General Description

The LM2687 CMOS Negative Regulated Switched Capacitor

Voltage Inverter delivers a very low noise adjustable output

for an input voltage in the range of +2.7V to +5.5V. Four low

cost capacitors are used in this circuit to provide up to 10mA

of output current. The regulated output for the LM2687 is

adjustable between −1.5V and −5.2V. The LM2687 operates

at 100 kHz (typical) switching frequency to reduce output

resistance and voltage ripple. With an operating current of

only 500 µA (charge pump power efficiency greater than

90% with most loads) and 0.05 µA typical shutdown current,

the LM2687 provides ideal performance for cellular phone

power amplifier bias and other low current, low noise nega-

tive voltage needs. The device comes in a small 8-pin MSOP

or LLP package.

Features

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Inverts and regulates the input supply voltage

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Small MSOP-8 or LLP-8 package

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91% typical charge pump power efficiency at 10mA

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Low output ripple (1mV typical)

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Shutdown lowers Quiescent current to 0.05 µA (typical)

Applications

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Wireless Communication Systems

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Cellular Phone Power Amplifier Biasing

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Interface Power Supplies

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Handheld Instrumentation

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Laptop Computers and PDA’s

Typical Application Circuit

10118001

Connection Diagrams

8-Pin MSOP

8-Pin LLP

10118002

10118025

April 2003

© 2003 National Semiconductor Corporation

DS101180

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