LM3243_16 Datasheet, PDF (1/32 Pages) Texas Instruments – High-Current Step-Down Converter

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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
•1 Input Voltage Range: 2.7 V to 5.5 V
• High-Efficiency PFM and PWM Modes With
Internal Synchronous Rectification
• Analog Bypass Function with Low Dropout
Resistance (45 mΩ Typical)
• Dynamically Adjustable Output Voltage: 0.4 V to
3.6 V (Typical) in PFM and PWM Modes
• Maximum Load Current: 2.5 A in PWM Mode
• PWM Switching Frequency: 2.7 MHz (Average)
• Modulated Switching Frequency to Aid Rx Band
Compliance
• Operates From a Single Li-ion Cell
(2.7 V to 5.5 V)
• Current and Thermal Overload Protection
• ACB Reduces Inductor Requirements and Size
• Minimum Total Solution Size by Using Small
Footprint and Case Size Inductor and Capacitors
2 Applications
• Cellular Phones
• Hand-Held Radios
• RF PC Cards
• Battery-Powered RF Devices
3 Description
The LM3243 is a DC-DC converter optimized for
powering multi-mode 2G, 3G, and 4G RF power
amplifiers (PAs) from a single Lithium-Ion cell. The
LM3243 steps down an input voltage from 2.7 V to
5.5 V to a dynamically adjustable output voltage of
0.4 V to 3.6 V. The output voltage is set through a
VCON analog input that adjusts the output voltage to
ensure efficient operation at all power levels of the
RF PA.
The LM3243 operates in constant frequency PWM
mode producing a small and predictable amount of
output voltage ripple. This enables best ECTEL
power requirements in GMSK and EDGE spectral
compliance, with the minimal amount of filtering and
excess headroom. When operating in PFM mode, the
LM3243 enables the lowest DG09 current
consumption and therefore maximizes system
efficiency.
The LM3243 has a unique Active Current assist and
analog Bypass (ACB) feature to minimize inductor
size without any loss of output regulation for the
entire battery voltage and RF output power range,
until dropout. ACB provides a parallel current path,
when needed, to limit the maximum inductor current
to 1.4 A (typical) while still driving a 2.5-A load. The
ACB also enables operation with minimal dropout
voltage. When considering using the LM3243 in a
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.
VBATT
10 µF
GPO1
GPO2
DAC
BB or
RFIC
Typical System Application Diagram
EN
PVIN VDD
SW
BP
LM3243
FB
MODE
ACB
VCON _{PGND SGND BGND}
1.5 µH
VOUT
10 µF
VCC_PA_3G
1.0 µF
VCC_PA_2G
4.7 µF
PA(s)
PA
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.