LM2618

400mA Sub-miniature, High Efficiency, Synchronous

PWM & PFM Programmable DC-DC Converter

General Description

The LM2618 step-down DC-DC converter is optimized for

powering low voltage circuits from a single Lithium-Ion cell. It

provides up to 400mA (300mA for B grade), over an input

voltage range of 2.8V to 5.5V. Pin programmable output

voltages of 1.80V, 1.83V, 1.87V or 1.92V allow adjustment

for MPU voltage options without board redesign or external

feedback resistors. Internal synchronous rectification pro-

vides high efficiency in both PWM and PFM operation.

The device has three pin-selectable modes for maximizing

battery life in mobile phones and similar portable applica-

tions. Low-noise PWM mode offers 600kHz fixed-frequency

operation to reduce interference in RF and data acquisition

applications during full-power operation. A SYNC input al-

lows synchronizing the switching frequency in a range of

500kHz to 1MHz to avoid noise from intermodulation with

system frequencies. Low-current hysteretic PFM mode re-

duces quiescent current to 180 µA (typ.) during system

standby. Shutdown mode turns the device off and reduces

battery consumption to 0.02µA (typ.). Additional features

include soft start and current overload protection.

The LM2618 is available in a 10 pin micro SMD packge. This

package uses National’s wafer level chip-scale micro SMD

technology and offers the smallest possible size. Only three

small external surface-mount components, an inductor and

two ceramic capacitors are required.

Key Specifications

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Operates from a single LiION cell (2.8V to 5.5V)

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Internal synchronous rectification provides high

efficiency in both PWM and PFM

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Pin programmable output voltage (1.80V, 1.83V, 1.87V

and 1.92V)

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400mA maximum load capability (300mA for B grade)

2% PWM mode DC output voltage precision

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5mV typ PWM mode output voltage ripple

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180 µA typ PFM mode quiescent current

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0.02µA typ shutdown mode current

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Internal synchronous rectification for high efficiency

(91% at 3.0V

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600kHz PWM mode switching frequency

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SYNC input for PWM mode frequency synchronization

from 500kHz to 1MHz

Features

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Sub-miniature 10-pin micro SMD package

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Only three tiny surface-mount external components

required

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Uses small ceramic capacitors.

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Internal soft start

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Current overload protection

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Thermal Shutdown Protection

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No external compensation required

Applications

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Mobile Phones

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Hand-Held Radios

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Battery Powered Devices

Typical Application Circuit

20036402

September 2002

© 2002 National Semiconductor Corporation

DS200364

www.national.com