JAJU299A June   2017  – January 2023

 

  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
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 TPS82130
    3. 2.3 Design Considerations
      1. 2.3.1 Inverting Buck-Boost Topology Concept
      2. 2.3.2 VIN and VOUT Range
      3. 2.3.3 Maximum Output Current
        1. 2.3.3.1 Thermal Limits
        2. 2.3.3.2 Stability Limits and Output Capacitor Selection
      4. 2.3.4 Design Precautions
      5. 2.3.5 Enable Pin Configuration
      6. 2.3.6 Power Good Pin Configuration
      7. 2.3.7 Discharging Output Voltage
      8. 2.3.8 Adjustable Soft-Start Time
      9. 2.3.9 Input Capacitor Selection
  8. 3Getting Started Hardware
  9. 4Testing and Results
  10. 5Design Files
    1. 5.1 Schematics
    2. 5.2 Bill of Materials
    3. 5.3 PCB Layout Recommendations
      1. 5.3.1 Layout Prints
    4. 5.4 Gerber Files
    5. 5.5 Assembly Drawings
  11. 6Related Documentation
  12. 7Trademarks
  13. 8Revision History

Input Capacitor Selection

An input capacitor, CIN, is required to provide a local bypass for the input voltage source. A low equivalent series resistance (ESR) X5R or X7R ceramic capacitor is best for input voltage filtering and minimizing interference with other circuits. For most applications, a 10-µF ceramic capacitor is recommended from VIN to ground (system ground, not –VOUT). The CIN capacitor value can be increased without any limit for better input voltage filtering.

For the inverting buck-boost configuration of the TPS82130, TI does not recommend installing a capacitor from VIN to –VOUT. Such a capacitor, if installed, provides an AC path from VIN to –VOUT. When VIN is applied to the circuit, this dV/dt across a capacitor from VIN to –VOUT creates a current that must return to ground (the return of the input supply) to complete its loop. This current may flow through the body diode of the internal low-side MOSFET and the inductor to return to ground. Flowing through the body diode pulls the VOUT pin below IC ground, which violates its absolute maximum rating. Such a condition may damage the TPS82130 and is not recommended; therefore, a capacitor from VIN to –VOUT is not required or recommended. If such a capacitor (CBP) is present, then a Schottky diode must be installed on the output, as the schematic in Figure 2-9 shows.

GUID-6620ED20-5A9B-49D1-9FB8-4DB19C6A4F07-low.svgFigure 2-9 Installation of Schottky Diode D1 Required, if Installing CBP