LM3243

PVIN VDD

SW

FB

VCON

PGND SGND

EN

MODE

VBATT

VOUT

ACB

BP

VCC_PA_2G

BB or

RFIC

DAC

GPO2

GPO1

BGND

1.5 µH

10 µF

1.0 µF

PA

4.7 µF

PA(s)

VCC_PA_3G

10 µF

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LM3243

SNVS782C – OCTOBER 2010 – REVISED AUGUST 2015

LM3243 High-Current Step-Down Converter for 2G, 3G, and 4G RF Power Amplifiers

1 Features

3 Description

The LM3243 is a DC-DC converter optimized for

1

•

Input Voltage Range: 2.7 V to 5.5 V

powering multi-mode 2G, 3G, and 4G RF power

•

High-Efficiency PFM and PWM Modes With

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

Internal Synchronous Rectification

LM3243 steps down an input voltage from 2.7 V to

•

Analog Bypass Function with Low Dropout

5.5 V to a dynamically adjustable output voltage of

0.4 V to 3.6 V. The output voltage is set through a

Resistance (45 m

Ω Typical)

VCON analog input that adjusts the output voltage to

•

Dynamically Adjustable Output Voltage: 0.4 V to

ensure efficient operation at all power levels of the

3.6 V (Typical) in PFM and PWM Modes

RF PA.

•

Maximum Load Current: 2.5 A in PWM Mode

The LM3243 operates in constant frequency PWM

•

PWM Switching Frequency: 2.7 MHz (Average)

mode producing a small and predictable amount of

•

Modulated Switching Frequency to Aid Rx Band

output voltage ripple. This enables best ECTEL

Compliance

power requirements in GMSK and EDGE spectral

compliance, with the minimal amount of filtering and

•

Operates From a Single Li-ion Cell

excess headroom. When operating in PFM mode, the

(2.7 V to 5.5 V)

LM3243

enables

the

lowest

DG09

current

•

Current and Thermal Overload Protection

consumption

and

therefore

maximizes

system

•

ACB Reduces Inductor Requirements and Size

efficiency.

•

Minimum Total Solution Size by Using Small

The LM3243 has a unique Active Current assist and

Footprint and Case Size Inductor and Capacitors

analog Bypass (ACB) feature to minimize inductor

size without any loss of output regulation for the

2 Applications

entire battery voltage and RF output power range,

until dropout. ACB provides a parallel current path,

•

Cellular Phones

when needed, to limit the maximum inductor current

•

Hand-Held Radios

to 1.4 A (typical) while still driving a 2.5-A load. The

•

RF PC Cards

ACB also enables operation with minimal dropout

voltage. When considering using the LM3243 in a

•

Battery-Powered RF Devices

system design, see the Layout section of this data

sheet.

Device Information(1)

PART NUMBER

PACKAGE

BODY SIZE (MAX)

LM3243

DSBGA (16)

2.049 mm × 2.049 mm

(1) For all available packages, see the orderable addendum at

the end of the data sheet.

Typical System Application Diagram

1

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.