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 ad-

justable between −1.5V and −5.2V. The LM2687 operates at

100 kHz (typical) switching frequency to reduce output resis-

tance 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 negative volt-

age needs. The device comes in a small 8-pin MSOP pack-

age.

Features

n Inverts and regulates the input supply voltage

n Small MSOP-8 package

n 91% typical charge pump power efficiency at 10mA

n Low output ripple (1mV typical)

n Shutdown lowers Quiescent current to 0.05 µA (typical)

Applications

n Wireless Communication Systems

n Cellular Phone Power Amplifier Biasing

n Interface Power Supplies

n Handheld Instrumentation

n Laptop Computers and PDA’s

Typical Application Circuit

Connection Diagram

DS101180-1

8-Pin MSOP

DS101180-2

August 1999

© 1999 National Semiconductor Corporation

DS101180

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