LM2681 Switched Capacitor Voltage Converter
March 1999
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
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Doubles or Splits Input Supply Voltage
SOT23-6 Package
15Ω Typical Output Impedance
90% Typical Conversion Efficiency at 20 mA
Applications
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Cellular Phones
Pagers
PDAs
Operational Amplifier Power Suppliers
Interface Power Suppliers
Handheld Instruments
Basic Application Circuits
Voltage Doubler
DS100965-1
Splitting V
in
in Half
DS100965-2
© 1999 National Semiconductor Corporation
DS100965
www.national.com
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