SNVS227H February   2003  – January 2015 LP3872 , LP3875

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 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 Shutdown (SD)
      2. 7.3.2 Load Voltage Sense
      3. 7.3.3 Short-Circuit Protection
      4. 7.3.4 Low Dropout Voltage
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
      3. 7.4.3 ERROR Flag Operation
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Dropout Voltage
      2. 8.1.2 Reverse Current Path
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Power Dissipation and Device Operation
        2. 8.2.2.2 External Capacitors
        3. 8.2.2.3 Selecting a Capacitor
        4. 8.2.2.4 Capacitor Characteristics
          1. 8.2.2.4.1 Ceramic
          2. 8.2.2.4.2 Tantalum
          3. 8.2.2.4.3 Aluminum
        5. 8.2.2.5 Turnon Characteristics for Output Voltages Programmed to 2 V or Less
        6. 8.2.2.6 RFI/EMI Susceptibility
        7. 8.2.2.7 Output Noise
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 Related Links
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ

10 Layout

10.1 Layout Guidelines

Good PC layout practices must be used or instability can be induced because of ground loops and voltage drops. The input and output capacitors must be directly connected to the input, output, and ground pins of the regulator using traces which do not have other currents flowing in them (Kelvin connect).

The best way to do this is to lay out CIN and COUT near the device with short traces to the IN, OUT, and GND pins. The regulator ground pin should be connected to the external circuit ground so that the regulator and its capacitors have a single-point ground.

It should be noted that stability problems have been seen in applications where vias to an internal ground plane were used at the ground points of the IC and the input and output capacitors. This was caused by varying ground potentials at these nodes resulting from current flowing through the ground plane. Using a single-point ground technique for the regulator and it's capacitors fixed the problem.

Because high current flows through the traces going into VIN and coming from VOUT, Kelvin connect the capacitor leads to these pins so there is no voltage drop in series with the input and output capacitors.

10.2 Layout Examples

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