LM3668 Datasheet, PDF (1/16 Pages) National Semiconductor (TI) – 1A, High Efficiency Dual Mode Single Inductor Buck-Boost DC/DC Converter

July 2007
LM3668
1A, High Efficiency Dual Mode Single Inductor Buck-Boost
DC/DC Converter
General Description
The LM3668 is a synchornous buck-boost DC-DC converter
optimized for powering low voltage circuits from a Li-Ion bat-
tery and input voltage rails between 2.5V and 5.5V. It has the
capability to support up to 1A output current over a output
voltage range of 2.8V/3.3V. The LM3668 regulates the output
voltage over the complete input voltage range by automati-
cally switching between buck or boost modes depending on
the input voltage.
The LM3668 has 2 N-channel MOSFETS and 2 P-channel
MOSFETS arranged in a topology that provides continuous
operation through the buck and boost operating modes.
There is a MODE pin that allows the user to choose between
an intelligent automatic PFM-PWM mode operation and
forced PWM operation. During PWM mode, a fixed-frequency
2.2MHz (typ.) is used. PWM mode drives load up to 1A. Hys-
teretic PFM mode extends the battery life through reduction
of the quiescent current to 45µA (typ.) at light loads during
system standby. Internal synchronous rectification provides
high efficiency. In shutdown mode (Enable pin pulled low) the
device turns off and reduces battery consumption to 0.01µA
(typ.).
The LM3668 is available in a 12-pin LLP package. A high
switching frequency of 2.2MHz (typ.) allows the use of tiny
surface-mount components including a 2.2µH inductor, a
10µF input capacitor, and a 22µF output capacitor.
Features
■ ^{45µA typical quiescent current}
■ ^{1A maximum load current for V}_IN ^{= 2.8V to 5.5V}
■ ^{800mA maximum load current for V}_IN ^{= 2.7V}
■ ^{600mA maximum load current for V}_IN ^{= 2.5V}
■ ^{2.2 MHz PWM fixed switching frequency (typ.)}
■ ^{Automatic PFM-PWM Mode or Forced PWM Mode}
■ ^{Wide Input Voltage Range: 2.5V to 5.5V}
■ ^{Output Voltage Range: 2.8V/3.3V}
■ ^{Internal synchronous rectification for high efficiency}
■ ^{Internal soft start: 600µs Maximum start-up time}
■ ^{0.01µA typical shutdown current}
■ ^{Current overload and Thermal shutdown protection}
■ ^{Frequency Sync Pin: 1.6Mhz to 2.7MHz}
Applications
■ ^{Handset Peripherals}
■ ^{MP3 players}
■ ^{Pre-Regulation for linear regulators}
■ ^PDAs
■ ^{Portable Hard Disk Drives}
■ ^{WiMax Modems}
Typical Applications
Typical Application Circuit
20191401
20191425
Efficiency at 3.3V Output
© 2007 National Semiconductor Corporation 201914
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