LM2687 Low Noise Regulated Switched Capacitor Voltage Inverter
August 1999
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 鈭?.5V and 鈭?.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 碌A (charge pump power efficiency greater than 90%
with most loads) and 0.05 碌A 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
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Inverts and regulates the input supply voltage
Small MSOP-8 package
91% typical charge pump power efficiency at 10mA
Low output ripple (1mV typical)
Shutdown lowers Quiescent current to 0.05 碌A (typical)
Applications
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Wireless Communication Systems
Cellular Phone Power Amplifier Biasing
Interface Power Supplies
Handheld Instrumentation
Laptop Computers and PDA鈥檚
Typical Application Circuit
DS101180-1
Connection Diagram
8-Pin MSOP
DS101180-2
漏 1999 National Semiconductor Corporation
DS101180
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