JAJU855 November   2022 TPS51215A

 

  1.   概要
  2.   リソース
  3.   特長
  4.   アプリケーション
  5.   5
  6. 1System Description
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 DCR current sense
      2. 2.2.2 Subtract and Amplify
      3. 2.2.3 Active Voltage Scale
      4. 2.2.4 IMON Output
    3. 2.3 Highlighted Products
    4. 2.4 System Design Theory
      1. 2.4.1 DCR Current Sense
      2. 2.4.2 Subtract and Amplify
      3. 2.4.3 Active Voltage Scale
      4. 2.4.4 IMON Output
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1. 3.3.1 Start-up
      2. 3.3.2 VID Change
      3. 3.3.3 Load Transient
      4. 3.3.4 Load-Line Test
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
      3. 4.1.3 PCB Layout Recommendations
      4. 4.1.4 Altium Project
      5. 4.1.5 Gerber Files
      6. 4.1.6 Assembly Drawings
    2. 4.2 Documentation Support
    3. 4.3 サポート・リソース
    4. 4.4 Trademarks
  10. 5About the Authors

2.2.2 Subtract and Amplify

Inductors with small DCR are always used for TPS51215A due to large current rating of VCCIN_AUX rail. So the sensed DCR voltage amplitude is small and the amplification is needed to implement. At the same time, the sensed voltage is a signal referenced to Vout and floating to ground. To get the sensed current signal used for active voltage scaling, it needs to be converted to a signal referenced to ground. Those two functions are achieved with an operational amplifier.