SBVS343 March   2019 TPS7A78

ADVANCE INFORMATION for pre-production products; subject to change without notice.  

  1. Features
  2. Applications
    1.     Typical Schematic
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
    1.     Pin Functions
  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 Timing Requirements
    7. 6.7 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Active Bridge Control
      2. 7.3.2 Full Bridge (FB) and Half Bridge Configurations
      3. 7.3.3 4 to 1 Switch Capacitor Voltage Reduction
      4. 7.3.4 VLDO_IN Overvoltage Protection
      5. 7.3.5 Dropout Voltage Regulation
      6. 7.3.6 Current Limit
      7. 7.3.7 Programmable Power-Fail Detection
      8. 7.3.8 Power-Good (PG) Detection
      9. 7.3.9 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation: AC Input mode
      2. 7.4.2 Dropout Mode
      3. 7.4.3 Disabled Mode
      4. 7.4.4 Normal Operation: DC Input mode
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Recommended Capacitor Types
      2. 8.1.2 Cap-Drop Capacitor CS
      3. 8.1.3 Surge Resistor RS
      4. 8.1.4 Input and Output Capacitors Requirements
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 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)
発注情報

Surge Resistor RS

The value of the minimum surge resistor RS (min) is determined by the peak AC supply voltage of the application. The value can be calculated using Equation 3, where VAC_MAX is the peak AC supply voltage for the application, and ISurge is the max AC transient current that TPS7A78 pin AC- or AC+ pins can tolerate as specified in the Recommended Operating Conditions table.

Equation 3. RS (min) = VAC_MAX ÷ I Surge

NOTE

The Maximum AC supply voltage is bound by the availability of high voltage cap-drop capacitor CS. As for surge resistors RS value shall be << 1/(2πf×CS). If RS value is comparable or higher than the reactance of CS, then the max output current will be limited by both components rather than just by CS.

If the solution requires the use of Transient Voltage Surge Suppressor (TVS) or a Metal-Oxide Varistors (MOV), then the minimum value of the surge resistor RS (min) can be calculated using the max clamping voltage of the TVS/MOV which is used for the solution. Table 2 provides the values for RS (min) resistor for a standard AC supply, use Equation 3 should your application has a different max AC supply voltage.