MOSFET

CONTROL

LOGIC

OSCILLATOR

SHUTDOWN

CONTROL

PWM

COMP

FB

EN

PGND

SW

SGND

BYP

ERROR

AMPLIFIER

~

CURRENT

SENSE

MAIN CONTROL

0.15V

DETECTOR

OVP

COMP

BYPOUT

LM3203

www.ti.com

SNVS355D – MAY 2005 – REVISED APRIL 2013

BLOCK DIAGRAM

OPERATION DESCRIPTION

The LM3203 is a simple, step-down DC-DC converter with a bypass switch, optimized for powering RF power

amplifiers (PAs) in mobile phones, portable communicators, and similar battery powered RF devices. It is

designed to allow the RF PA to operate at maximum efficiency over a wide range of power levels from a single

Li-Ion battery cell. It is based on current-mode buck architecture, with synchronous rectification for high

efficiency. It is designed for a maximum load capability of 500mA. Maximum load range may vary from this

depending on input voltage, output voltage and the inductor chosen.

The device has all three of the pin-selectable operating modes required for powering RF PAs in mobile phones

and other sophisticated portable device with complex power management needs. Fixed-frequency PWM

operation offers regulated output at high efficiency while minimizing interference with sensitive IF and data

acquisition circuits. Bypass mode turns on an internal FET bypass switch to power the PA directly from the

battery. This helps the RF power amplifier maintain its operating power during low battery conditions by reducing

the dropout voltage across the LM3203. Shutdown mode turns the device off and reduces battery consumption to

0.1µA (typ.).

load with 3.2V output, 3.6V input. PWM mode quiescent current is 0.675 mA (typ.). The FB pin voltage is

can change the output voltge range. This ensures longer battery life by being able to change the PA supply

voltage dynamically depending on its transmitting power.

Additional features include current overload protection, over voltage protection and thermal shutdown.

The LM3203 is constructed using a chip-scale 10-pin DSBGA package. This package offers the smallest

possible size, for space-critical applications such as cell phones, where board area is an important design

consideration. Use of a high switching frequency (2MHz typ.) reduces the size of external components. Use of a

DSBGA package requires special design considerations for implementation. (See DSBGA Package Assembly

and Use section.) Its fine bump-pitch requires careful board design and precision assembly equipment. Use of

this package is best suited for opaque-case applications, where its edges are not subject to high-intensity

ambient red or infrared light. Also, the system controller should set EN low during power-up and other low supply

voltage conditions. (See Shutdown Mode section.)

Copyright © 2005–2013, Texas Instruments Incorporated

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Product Folder Links: LM3203