ZHCSH22C January   2009  – November 2017 LM3241

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      典型应用
  4. 4 修订历史记录
  5. 5 Pin Configuration and Functions
    1.     Pin 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 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 Circuit Operation
      2. 7.3.2 Internal Synchronization Rectification
      3. 7.3.3 Current Limiting
      4. 7.3.4 Dynamically Adjustable Output Voltage
      5. 7.3.5 Thermal Overload Protection
      6. 7.3.6 Soft Start
    4. 7.4 Device Functional Modes
      1. 7.4.1 PWM Mode Operation
      2. 7.4.2 Eco-mode™ Operation
      3. 7.4.3 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 Setting the Output Voltage
        2. 8.2.2.2 Inductor Selection
          1. 8.2.2.2.1 Method 1
          2. 8.2.2.2.2 Method 2
        3. 8.2.2.3 Capacitor Selection
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 DSBGA Package Assembly and Use
      2. 10.1.2 Board Layout Considerations
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 文档支持
      1. 11.1.1 相关文档
    2. 11.2 接收文档更新通知
    3. 11.3 社区资源
    4. 11.4 商标
    5. 11.5 静电放电警告
    6. 11.6 Glossary
  12. 12机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

7.1 Overview

The LM3241 is a simple, step-down DC-DC converter optimized for powering RF power amplifiers (PAs) in mobile phones, portable communicators, and similar battery-powered RF devices. The device 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. The design is based on a voltage-mode buck architecture, with synchronous rectification for high efficiency. The device is designed for a maximum load capability of 750 mA in PWM mode. Maximum load range may vary from this depending on input voltage, output voltage, and the inductor chosen.

Three modes of operation are available depending on the current required: pulse width modulation (PWM), Eco-mode (economy mode), and shutdown. The LM3241 operates in PWM mode at higher load-current conditions. Lighter loads cause the device to automatically switch into Eco-mode. Shutdown mode turns off the device and reduces battery consumption to 0.1 µA (typical).

Precision of the DC PWM-mode output voltage is ±2% for 3.4 VOUT. Efficiency is around 95% (typical) for a 500-mA load with a 3.3-V output and 3.9-V input. The output voltage is dynamically programmable from 0.6 V to 3.4 V by adjusting the voltage on the control pin (VCON) without the need for external feedback resistors. This feature 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 and thermal overload shutdown.

The LM3241 is constructed using a chip-scale, 6-bump 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 (6 MHz, typical) reduces the size of external components. As shown in Figure 29, only three external power components are required for implementation. Use of a DSBGA package requires special design considerations for implementation (for more information see the DSBGA Package Assembly and Use section.) The fine-bump pitch of the package 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 the Shutdown Mode section).