ZHCSD73D August   2012  – August 2018 LMZ21700

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      简化原理图
      2.      VIN = 12V 时的效率
  4. 4 修订历史记录
  5. 5 Pin Configuration and Functions
    1. Table 1. Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Package Construction
    4. 7.4 Feature Description
      1. 7.4.1 Input Under Voltage Lockout
      2. 7.4.2 Enable Input (EN)
      3. 7.4.3 Softstart and Tracking Function (SS)
      4. 7.4.4 Power Good Function (PG)
      5. 7.4.5 Output Voltage Setting
      6. 7.4.6 Output Current Limit and Output Short Circuit Protection
      7. 7.4.7 Thermal Protection
    5. 7.5 Device Functional Modes
      1. 7.5.1 PWM Mode Operation
      2. 7.5.2 PSM Operation
  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 Input Capacitor (CIN)
        2. 8.2.2.2 Output Capacitor (COUT)
        3. 8.2.2.3 Softstart Capacitor (CSS)
        4. 8.2.2.4 Power Good Resistor (RPG)
        5. 8.2.2.5 Feedback Resistors (RFBB and RFBT)
      3. 8.2.3 Application Curves
        1. 8.2.3.1 VOUT = 1.2 V
        2. 8.2.3.2 VOUT = 1.8 V
        3. 8.2.3.3 VOUT = 2.5 V
        4. 8.2.3.4 VOUT = 3.3 V
        5. 8.2.3.5 VOUT = 5.0 V
    3. 8.3 Do's and Don'ts
  9. 9 Power Supply Recommendations
    1. 9.1 Voltage Range
    2. 9.2 Current Capability
    3. 9.3 Input Connection
      1. 9.3.1 Voltage Drops
      2. 9.3.2 Stability
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Minimize the High di/dt Loop Area
      2. 10.1.2 Protect the Sensitive Nodes in the Circuit
      3. 10.1.3 Provide Thermal Path and Shielding
    2. 10.2 Layout Example
      1. 10.2.1 High Density Layout Example for Space Constrained Applications
        1. 10.2.1.1 35 mm² Solution Size (Single Sided)
  11. 11器件和文档支持
    1. 11.1 器件支持
    2. 11.2 开发支持
      1. 11.2.1 使用 WEBENCH® 工具创建定制设计
    3. 11.3 接收文档更新通知
    4. 11.4 社区资源
    5. 11.5 商标
    6. 11.6 静电放电警告
    7. 11.7 术语表
  12. 12机械、封装和可订购信息
    1. 12.1 Tape and Reel Information

封装选项

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)
  • SIL|8
散热焊盘机械数据 (封装 | 引脚)
订购信息

7.4.3 Softstart and Tracking Function (SS)

When EN is set high for device operation the LMZ21700 will start switching after 50 μs delay and the output voltage will start rising. The VOUT rising slope is controlled by the external capacitor CSS connected to the softstart (SS) pin. The nano module has a 2.5 μA constant current source internally connected to the SS pin to program the softstart time TSS:

Equation 1. TSS = CSS x 1.25 V / 2.5 μA

The softstart capacitor voltage is reset to zero volts when EN is pulled low and when the thermal protection is active.

If tracking function is desired, the SS pin can be used to track external voltage. If the applied external tracking voltage is between 100 mV and 1.2 V, the FB voltage will follow SS according to the following relationship:

Equation 2. VFB = 0.64 x VSS
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