LM3668_0809 Datasheet, PDF (1/18 Pages) National Semiconductor (TI) – 1A, High Efficiency Dual Mode Single Inductor Buck-Boost DC/DC Converter

September 10, 2008
LM3668
1A, High Efficiency Dual Mode Single Inductor Buck-Boost
DC/DC Converter
General Description
The LM3668 is a synchronous 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 the output
voltage range. The LM3668 regulates the output voltage over
the complete input voltage range by automatically switching
between buck or boost modes depending on the input volt-
age.
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}
■ ^{For 2.8V/3.3V and 3.0/3.4V versions:}
- 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
■ ^{For 4.5/5V}
- 1A maximum load current for V_IN = 3.9V to 5.5V
- 800mA maximum load current for V_IN = 3.4V to 3.8V
- 700mA maximum load current for V_IN = 3.0V to 3.3V
- 600mA maximum load current for V_IN = 2.7V to 2.9V
■ ^{2.2MHz PWM fixed switching frequency (typ.)}
■ ^{Automatic PFM-PWM Mode or Forced PWM Mode}
■ ^{Wide Input Voltage Range: 2.5V to 5.5V}
■ ^{Internal synchronous rectification for high efficiency}
■ ^{Internal soft start: 600µs Maximum start-up time after V}_IN
settled
■ ^{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
© 2008 National Semiconductor Corporation 201914
Efficiency at 3.3V Output
20191476
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