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.