ZHCSM29A September   2023  – June 2024 LM70840-Q1 , LM70860-Q1 , LM70880-Q1

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 说明（续）
  6. 5 Pin Configuration and Functions
  7. 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 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Input Voltage Range (VIN)
      2. 7.3.2  High-Voltage Bias Supply Regulator (VCC, BIAS, VDDA)
      3. 7.3.3  Enable (EN)
      4. 7.3.4  Power-Good Monitor (PG)
      5. 7.3.5  Switching Frequency (RT)
      6. 7.3.6  Dual Random Spread Spectrum (DRSS)
      7. 7.3.7  Soft Start
      8. 7.3.8  Output Voltage Setpoint (FB)
      9. 7.3.9  Minimum Controllable On-Time
      10. 7.3.10 Error Amplifier and PWM Comparator (FB, EXTCOMP)
      11. 7.3.11 Slope Compensation
      12. 7.3.12 Shunt Current Sensing
      13. 7.3.13 Hiccup Mode Current Limiting
      14. 7.3.14 Device Configuration (CONFIG)
      15. 7.3.15 Single-Output Dual-phase Operation
      16. 7.3.16 Pulse Frequency Modulation (PFM) / Synchronization
      17. 7.3.17 Thermal Shutdown (TSD)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Standby Mode
      3. 7.4.3 Active Mode
      4. 7.4.4 Sleep Mode
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Power Train Components
        1. 8.1.1.1 Buck Inductor
        2. 8.1.1.2 Output Capacitors
        3. 8.1.1.3 Input Capacitors
        4. 8.1.1.4 EMI Filter
      2. 8.1.2 Error Amplifier and Compensation
      3. 8.1.3 Maximum Ambient Temperature
        1. 8.1.3.1 Derating Curves
    2. 8.2 Typical Applications
      1. 8.2.1 Design 1 – High Efficiency, Wide Input, 400-kHz Synchronous Buck Regulator
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 8.2.1.2.2 Custom Design With Excel Quickstart Tool
          3. 8.2.1.2.3 Buck Inductor
          4. 8.2.1.2.4 Current-Sense Resistance
          5. 8.2.1.2.5 Output Capacitors
          6. 8.2.1.2.6 Input Capacitors
          7. 8.2.1.2.7 Frequency Set Resistor
          8. 8.2.1.2.8 Feedback Resistors
          9. 8.2.1.2.9 Compensation Components
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Design 2 – High Efficiency 48V to 12V 400kHz Synchronous Buck Regulator
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Thermal Design and Layout
      3. 8.4.3 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
        1. 9.1.1.1 Custom Design With WEBENCH® Tools
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
        1. 9.2.1.1 PCB Layout Resources
        2. 9.2.1.2 Thermal Design Resources
    3. 9.3 接收文档更新通知
    4. 9.4 支持资源
    5. 9.5 Trademarks
    6. 9.6 静电放电警告
    7. 9.7 术语表
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

请参考 PDF 数据表获取器件具体的封装图。

机械数据 (封装 | 引脚)
  • RRX|29
散热焊盘机械数据 (封装 | 引脚)

7.3.3 Enable (EN)

The EN/UVLO pin can be connected to a voltage as high as 80V. The LM708x0-Q1 has a precision enable. When the EN pin is greater than 1V, the output is enabled. If the EN pin is pulled below 0.55V (typical), the LM708x0-Q1 is in shutdown with an IQ of 2.3μA (typical) current draw from VIN. When the enable voltage is between 0.55V (typical) and 1V (typical), the LM708x0-Q1 is in standby mode. When in standby mode, the VCC regulator is enabled, the device is not switching, and the IQ current is 350μA (typical). Users can also enable the LM708x0-Q1 with standard CMOS logic drivers. A voltage greater than 2.0V enables the LM708x0-Q1, and a voltage less than 0.4V disables the LM708x0-Q1. However, many applications benefit from using a resistor divider RUV1 and RUV2 as shown in Figure 7-2 to establish a precision UVLO threshold. TI recommends setting the input voltage turn-on threshold at 4.5V or higher when the rise time of the input supply to the LM708x0-Q1 is significantly slower than the internal soft-start time. TI does not recommend leaving the EN pin floating.

Use Equation 2 and Equation 3 to calculate the UVLO resistors given the required input turn-on voltage.

Equation 2. R UV 1 = V IN ( on ) V EN - TH – 1 × R UV 2
Equation 3. R UV 1 = V IN ( on ) V EN - TH – 1 × R UV 2
LM70840-Q1 LM70860-Q1 LM70880-Q1 Programmable Input Voltage UVLO Turn-on and Turn-off Figure 7-2 Programmable Input Voltage UVLO Turn-on and Turn-off
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