LM3203

Step-Down DC-DC Converter with Bypass Mode for

CDMA / WCDMA RF Power Amplifiers

General Description

The LM3203 is a DC-DC converter optimized for powering

RF power amplifiers (PAs) from a single Lithium-Ion cell.

However, they may be used in many other applications. It

steps down an input voltage of 2.7V to 5.5V to an adjustable

output voltage of 0.8V to 3.6V. The output voltage is set

using a V

optimizing efficiency of the RF PA at various power levels.

The LM3203 offers 3 modes for mobile phones and similar

RF PA applications. Fixed-frequency PWM mode minimizes

RF interference. Bypass mode turns on an internal bypass

switch to power the PA directly from the battery. Shutdown

mode turns the device off and reduces battery consumption

to 0.1µA (typ.).

The LM3203 is available in a 10-pin lead free micro SMD

package. A high switching frequency (2MHz) allows use of

tiny surface-mount components.

Features

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2MHz (typ.) PWM Switching Frequency

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Operates from a single Li-Ion cell (2.7V to 5.5V)

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Adjustable Output Voltage (0.8V to 3.6V)

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500mA Maximum load capability (PWM and Bypass

mode)

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PWM / Forced Bypass Mode

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Low R

Ω (typ.)

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High Efficiency (96% typ. at 3.6V

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Fast Turn-on time when Enabled (50µs typ.), 3GPP

Compliant

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10-pin micro SMD Package

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Current Overload Protection

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Thermal Overload Protection

Applications

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Cellular Phones

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Hand-Held Radios

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RF PC Cards

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Battery Powered RF Devices

Typical Application

20141601

July 2005

© 2005 National Semiconductor Corporation

DS201416

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