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

Input and Output Capacitors Requirements

All the capacitors seen in Typical Schematic are required for proper operation of the device. For switching caps CSC1 and CSC2 , use the required capacitors values along with their voltage rating as specified in the Recommended Operating Conditions table. Oversizing switch caps is not recommended since it will have an adverse affect on the start-up time of the whole solution. It will also lengthen the time taken by the over-voltage clamp to recover from an over-voltage event. Keep the switch caps as close to the device as possible to eliminate any unwanted trace inductance.

For bulk capacitor CSCIN, use a minimum voltage rating of 35 V for CSCIN to account for bias voltage capacitor derating. As for CSCIN size, use Equation 4 for FB 60 Hz input AC supply and Equation 5 for HB 60 Hz input AC supply.

Equation 4. CSCIN = 0.0014 × ILOAD
Equation 5. CSCIN = 0.0035 × ILOAD

Use Equation 6 for FB 50 Hz input AC supply and Equation 7 for HB 50 Hz input AC supply.

Equation 6. CSCIN = 0.0017 × ILOAD
Equation 7. CSCIN = 0.0041 × ILOAD

It is acceptable to round down the value calculated from the above equations to the nearest available standard capacitor value as long as it is with 10 % or less otherwise round up. It also recommended to oversize CSCIN and upscale its voltage rating to account for relatively low life expectancy especially when electrolytic capacitor is used. If your application requires a hold-up time, you can increase the size of CSCIN capacitor or CLDO_IN capacitor accordingly without exceeding the max CLDO_IN cap specified in the Recommended Operating Conditions table. Note that vastly oversizing CSCIN or CLDO_IN have an adverse effect on the startup time of the solution.

Use the minimum capacitors value specified in the Recommended Operating Conditions table if you application does not require a hold-up time. As for CLDO_OUT size, it is recommended to maintain 10:1 ratio between CLDO_IN and CLDO_OUT for application using close to maximum load current. For optimum device performance place capacitors as close a possible to the device.

Table 2. Components Selection Table for Various Usage Conditions

AC SUPPLY VRMS (Hz) RS (min) (Ω)(1) IOUT VLDO_OUT (V) CS (nF) CLDO_IN (µF) CLDO_OUT (µF)
FULL BRIDGE HALF BRIDGE
120 (60) 68 10 3.3, 3.6, 5.0 100 220 10(2) 1
30 330 470
60 560 1000
90 820
120 1000
240 (50) 131 10 3.3, 3.6, 5.0 47 100 10(2) 1
30 150 330
60 330 560
90 470
120 560
The value of surge resistor RS (min) is calculated based off the peak AC voltage of the supply. If a TVS/MOV is used, then the value of RS (min) should be calculated based off the max clamping voltage of the TVS/MOV.
For small load currents, a lower value of the CLDO_IN cap can be used