SLVSGG1A February   2022  – September 2022 TPS7H5005-SEP , TPS7H5006-SEP , TPS7H5007-SEP , TPS7H5008-SEP

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Electrical Characteristics: All Devices
    6. 7.6  Electrical Characteristics: TPS7H5005-SEP
    7. 7.7  Electrical Characteristics: TPS7H5006-SEP
    8. 7.8  Electrical Characteristics: TPS7H5007-SEP
    9. 7.9  Electrical Characteristics: TPS7H5008-SEP
    10. 7.10 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  VIN and VLDO
      2. 8.3.2  Start-Up
      3. 8.3.3  Enable and Undervoltage Lockout (UVLO)
      4. 8.3.4  Voltage Reference
      5. 8.3.5  Error Amplifier
      6. 8.3.6  Output Voltage Programming
      7. 8.3.7  Soft Start (SS)
      8. 8.3.8  Switching Frequency and External Synchronization
        1. 8.3.8.1 Internal Oscillator Mode
        2. 8.3.8.2 External Synchronization Mode
        3. 8.3.8.3 Primary-Secondary Mode
      9. 8.3.9  Primary Switching Outputs (OUTA/OUTB)
      10. 8.3.10 Synchronous Rectifier Outputs (SRA/SRB)
      11. 8.3.11 Dead Time and Leading Edge Blank Time Programmability (PS, SP, and LEB)
      12. 8.3.12 Pulse Skipping
      13. 8.3.13 Duty Cycle Programmability
      14. 8.3.14 Current Sense and PWM Generation (CS_ILIM)
      15. 8.3.15 Hiccup Mode Operation (HICC)
      16. 8.3.16 External Fault Protection (FAULT)
      17. 8.3.17 Slope Compensation (RSC)
      18. 8.3.18 Frequency Compensation
      19. 8.3.19 Thermal Shutdown
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1  Switching Frequency
        2. 9.2.2.2  Output Voltage Programming Resistors
        3. 9.2.2.3  Dead Time
        4. 9.2.2.4  Leading Edge Blank Time
        5. 9.2.2.5  Soft-Start Capacitor
        6. 9.2.2.6  Transformer
        7. 9.2.2.7  Main Switching FETs
        8. 9.2.2.8  Synchronous Rectificier FETs
        9. 9.2.2.9  RCD Clamp
        10. 9.2.2.10 Output Inductor
        11. 9.2.2.11 Output Capacitance and Filter
        12. 9.2.2.12 Sense Resistor
        13. 9.2.2.13 Hiccup Capacitor
        14. 9.2.2.14 Frequency Compensation Components
        15. 9.2.2.15 Slope Compensation Resistor
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information
    1. 13.1 Mechanical Data

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9.2.2.12 Sense Resistor

The converter was designed such that the cycle-by-cycle limiting will begin once the output current reaches roughly 35 A. Given that the peak inductor current at maximum load current is 24.25 A, this provides about 45% margin before an overcurrent event is detected by the controller. The primary side current is being sensed at CS_ILIM, so the turns ratio must be accounted for when calculating the necessary value of the sense resistor. Likewise, a current sense transformer with turns ratio of 1:100 is used to step down the primary current. The following calcuations are used to arrive at the value of RCS that translates to the desired output overcurrent level.

Equation 71.
Equation 72.
Equation 73.
Equation 74.

Based on the calculation, a 7.5-Ω resistor was selected for RCS.