ZHCS566I February   2010  – March 2022 LMZ12010

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  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 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 Output Overvoltage Protection
      2. 7.3.2 Current Limit
      3. 7.3.3 Thermal Protection
      4. 7.3.4 Prebiased Start-Up
    4. 7.4 Device Functional Modes
      1. 7.4.1 Discontinuous Conduction and Continuous Conduction Modes
  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 Enable Divider, RENT, RENB, and RENH Selection
        2. 8.2.2.2 Output Voltage Selection
        3. 8.2.2.3 Soft-Start Capacitor Selection
        4. 8.2.2.4 Tracking Supply Divider Option
        5. 8.2.2.5 COUT Selection
        6. 8.2.2.6 CIN Selection
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
    3. 10.3 Power Dissipation and Thermal Considerations
    4. 10.4 Power Module SMT Guidelines
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 第三方产品免责声明
      2. 11.1.2 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 支持资源
    4. 11.4 接收文档更新通知
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 术语表
  12. 12Mechanical, Packaging, and Orderable Information

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

8.2.2.6 CIN Selection

The LMZ12010 module contains two internal ceramic input capacitors. Additional input capacitance is required external to the module to handle the input ripple current of the application. The input capacitor can be several capacitors in parallel. This input capacitance must be located in very close proximity to the module. Input capacitor selection is generally directed to satisfy the input ripple current requirements rather than by capacitance value. Input ripple current rating is dictated by Equation 12:

Equation 12. GUID-59AF0DA8-0307-4432-BC3B-F25495496934-low.gif

where

  • D ≊ VOUT / VIN

As a point of reference, the worst case ripple current will occur when the module is presented with full load current and when VIN = 2 × VOUT.

Recommended minimum input capacitance is 30-µF X7R (or X5R) ceramic with a voltage rating at least 25% higher than the maximum applied input voltage for the application. TI also recommends to pay attention to the voltage and temperature derating of the capacitor selected.

Note:

Ripple current rating of ceramic capacitors may be missing from the capacitor data sheet and the user may have to contact the capacitor manufacturer for this parameter.

If the system design requires a certain minimum value of peak-to-peak input ripple voltage (ΔVIN) to be maintained then Equation 13 may be used.

Equation 13. GUID-7498B223-4E95-4934-BF27-055CB1D82FD1-low.gif

If ΔVIN is 200 mV or 1.66% of VIN for a 12-V input to 3.3-V output application and fSW = 350 kHz then:

Equation 14. GUID-EFCA3C60-6FEF-4274-BF53-B925AFDBBE74-low.gif

Additional bulk capacitance with higher ESR can be required to damp any resonant effects of the input capacitance and parasitic inductance of the incoming supply lines. The LMZ12010 typical applications schematic and evaluation board include a 150-μF 50-V aluminum capacitor for this function. There are many situations where this capacitor is not necessary.