SBVS343A March   2019  – September 2019 TPS7A78

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Schematic Half-Bridge Configuration
      2.      Typical Schematic Full-Bridge Configuration
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Timing Requirements
    7. 6.7 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 Active Bridge Control
      2. 7.3.2 Full-Bridge (FB) and Half-Bridge (HB) Configurations
      3. 7.3.3 4:1 Switched-Capacitor Voltage Reduction
      4. 7.3.4 Undervoltage Lockout Circuits (VUVLO_SCIN) and (VUVLO_LDO_IN)
      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
      2. 7.4.2 Dropout Mode
      3. 7.4.3 Disabled Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Recommended Capacitor Types
      2. 8.1.2 Input and Output Capacitors Requirements
      3. 8.1.3 Startup Behavior
      4. 8.1.4 Load Transient
      5. 8.1.5 Standby Power and Output Efficiency
      6. 8.1.6 Reverse Current
      7. 8.1.7 Switched-Capacitor Stage Output Impedance
      8. 8.1.8 Power Dissipation (PD)
      9. 8.1.9 Estimating Junction Temperature
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Calculating the Cap-Drop Capacitor CS
          1. 8.2.2.1.1 CS Calculations for the Typical Design
        2. 8.2.2.2 Calculating the Surge Resistor RS
          1. 8.2.2.2.1 RS Calculations for the Typical Design
        3. 8.2.2.3 Checking for the Device Maximum ISHUNT Current
          1. 8.2.2.3.1 ISHUNT Calculations for the Typical Design
        4. 8.2.2.4 Calculating the Bulk Capacitor CSCIN
          1. 8.2.2.4.1 CSCIN Calculations for the Typical Design
        5. 8.2.2.5 Calculating the PFD Pin Resistor Dividers for a Power-Fail Detection
          1. 8.2.2.5.1 PFD Pin Resistor Divider Calculations for the Typical Design
        6. 8.2.2.6 Summary of the Typical Application Design Components
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Evaluation Module
        2. 11.1.1.2 SIMPLIS Model
      2. 11.1.2 Device Nomenclature
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

3 Description

The TPS7A78 improves the overall efficiency and standby-power in power-supplies in an easy-to-use, non-magnetic approach to AC/DC conversion. The TPS7A78 uses a capacitor-drop architecture to lower the AC source voltage before actively clamping the rectified voltage. The device then regulates this rectified voltage down to the application-specific operating voltage. The unique architecture of the device allows the standby power to be reduced to just a few 10s of milliwatts. The TPS7A78 switched-capacitor stage reduces power losses by stepping down the rectified input voltage by a factor of four and increasing the output-to-input current by the same ratio, as given by PIN ≅ POUT and VIN ≅ VOUT × 4. Compared to a traditional capacitor-drop (cap-drop) stage, this step down reduces input current, thus minimizing the value of the capacitance needed.

Electricity-metering applications, where the power supply must be reliable and magnetic tamper-proof, benefits from using the TPS7A78 because this device does not require external magnetics. This feature makes complying with IEC 61000-4-8 easier while minimizing magnetic shielding cost.

Additionally, the TPS7A78 also comes with a user-programmable, power-fail detection threshold that can provide an early alert to power failures and enable shutdown before complete power loss. The power-good indicator (PG) is also provided for sequencing or resetting a microcontroller.

The TPS7A78 is available in a 14-pin HTSSOP (PWP) package.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
TPS7A78 HTSSOP (14) 5.00 mm × 6.50 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.