1 Features
1• Input Voltage Range: 2.5 V to 5.5 V
• Adjustable Output Voltages (VOUT): 0.7 V to 2.5 V
• Fixed Output Voltages: 1.2 V, 1.5 V, 1.6 V, 1.8 V,
1.875 V, 3.3V
• 15-μA Typical Quiescent Current
• 350-mA Maximum Load Capability
• 1-MHz PWM Fixed Switching Frequency (Typical)
• Automatic PFM and PWM Mode Switching
• Low Dropout Operation – 100% Duty Cycle Mode
• Internal Synchronous Rectification for High
Efficiency
• Internal Soft Start
• 0.1-μA Typical Shutdown Current
• Current Overload Protection
• Operates from a Single Li-Ion Cell or Three-Cell
NiMH/NiCd Batteries
• Only Three Tiny Surface-Mount External
Components Required (One Inductor, Two
Ceramic Capacitors)

2 Applications
• Mobile Phones and Handheld Devices
• PDAs
• Palm-Top PCs
• Portable Instruments
• Battery-Powered Devices

3 Description
The LM3670 step-down DC-DC converter is
optimized for powering ultralow voltage circuits from a
single Li-Ion cell or three-cell NiMH/NiCd batteries. It
provides up to 350-mA load current, over an input
voltage range from 2.5 V to 5.5 V. There are several
different fixed voltage output options available as well
as an adjustable output voltage version.
The device offers superior features and performance
for mobile phones and similar portable applications
with complex power management systems. Automatic
intelligent switching between pulse width modulation
(PWM) low-noise and pulse frequency modulation
(PFM) low-current mode offers improved system
control. During full-power operation, a fixed-frequency
1-MHz (typical) PWM mode drives loads from
approximately 70 mA to 350 mA maximum, with up to
95% efficiency. Hysteretic PFM mode extends the
battery life through reduction of the quiescent current
to 15 μA (typical) during light current loads and
system standby. Internal synchronous rectification
provides high efficiency (90% to 95% typical at loads
between 1 mA and 100 mA). In shutdown mode
(enable (EN) pin pulled low) the device turns off and
reduces battery consumption to 0.1 μA (typical).
The LM3670 is available in a 5-pin SOT-23 package.
A high switching frequency (1 MHz typical) allows use
of tiny surface-mount components. Only three
external surface-mount components, an inductor and
two ceramic capacitors, are required.