SNVS782C October   2010  – August 2015 LM3243

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5  Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 System Characteristics
    7. 6.7 Timing Requirements
    8. 6.8 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 ACB
      2. 7.3.2 Bypass Operation
      3. 7.3.3 Mode Pin
      4. 7.3.4 Dynamic Adjustment Of Output Voltage
      5. 7.3.5 Internal Synchronous Rectification
      6. 7.3.6 Current Limit
      7. 7.3.7 Timed Current Limit
      8. 7.3.8 Thermal Overload Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 PWM Operation
      2. 7.4.2 PFM Mode
      3. 7.4.3 Mode Selection
      4. 7.4.4 Shutdown Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Inductor Selection
        2. 8.2.2.2 Capacitor Selection
        3. 8.2.2.3 Setting The Output Voltage
          1. 8.2.2.3.1 DAC Control
          2. 8.2.2.3.2 PDM-Based VCON Signal
          3. 8.2.2.3.3 VCON Pin
        4. 8.2.2.4 EN Input Control
        5. 8.2.2.5 Start-Up
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 PCB Considerations
        1. 10.1.1.1 Energy Efficiency
        2. 10.1.1.2 EMI
      2. 10.1.2 Manufacturing Considerations
    2. 10.2 Layout Example
      1. 10.2.1 LM3243 RF Evaluation Board
      2. 10.2.2 DC-DC Converter Section
      3. 10.2.3 VBATT Star Supply Connection
    3. 10.3 DSBGA Package Assembly and Use
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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1 Features

  • 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.

Typical System Application Diagram

LM3243 30132101.gif