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




The TPS7A78 is a non-isolated smart linear voltage regulator that uses an external high voltage cap-drop capacitor (CS), and internally controlled active bridge rectifier to regulate to a DC voltage. The reactance of CS sets the maximum AC charging current that is used to charge the rectified AC voltage bulk capacitor CSCIN. The device also integrates a 4:1 switch cap stage which has the effect of reducing the input current by 1/4th. The surge resistors (RS) is used to limit the inrush current to the device. RS can also be used to protect the device from surge currents in conjunction with transient voltage suppresser (TVS) or a metal-oxide varistors (MOV). Unlike typical AC to DC power solutions, the TPS7A78 does not requires external magnetics which makes it an excellent choice for e-metering applications by making it more tamper resistant. The unique design of the device allows it to reduce the standby power to approximately 15 mW for light load applications while maintaining the device high efficiency.

The device features an internally controlled active bridge rectifier with Full Bridge and Half Bridge configuration, a 4:1 two stage switching capacitors voltage reduction, an over voltage (over charge) protection on VLDO_IN, internally controlled dropout voltage regulation, brick-wall current limit, thermal shutdown on VLDO_OUT, programable power fail detection, and power good detection. This device is a high efficiency AC to DC power solution that operates on an ambient temperature range from -40 °C to 125 °C.


TPS7A78 device can be powered off a DC supply directly on SCIN pin, (for 3.3 V output voltage and below), in case of AC supply failure or absence. When a DC supply is used to power the device, the internally controlled dropout voltage regulation will be affected as explained in the Dropout Voltage Regulation section.