SLVSHI9A March   2025  – September 2025 TPS7H5020-SEP , TPS7H5020-SP

PRODMIX  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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 Quality Conformance Inspection
    7. 6.7 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Input Voltage (VIN) and VLDO
      2. 7.3.2  Driver Input Voltage (PVIN)
      3. 7.3.3  Start-Up
      4. 7.3.4  Enable and Undervoltage Lockout (UVLO)
      5. 7.3.5  Voltage Reference
      6. 7.3.6  Error Amplifier
      7. 7.3.7  Output Voltage Programming
      8. 7.3.8  Soft Start (SS)
      9. 7.3.9  Switching Frequency and External Synchronization
        1. 7.3.9.1 Internal Oscillator Mode
        2. 7.3.9.2 External Synchronization Mode
          1. 7.3.9.2.1 External Synchronization with TPS7H5021
      10. 7.3.10 Duty Cycle Limit
      11. 7.3.11 Minimum On-Time and Off-Time
      12. 7.3.12 Pulse Skipping
      13. 7.3.13 Leading Edge Blank Time
      14. 7.3.14 Current Sense and PWM Generation (CS_ILIM)
      15. 7.3.15 Gate Driver Output
      16. 7.3.16 Unpowered Voltage Clamp
      17. 7.3.17 Sourcing Driver Return (OUTH_REF)
      18. 7.3.18 Slope Compensation (RSC)
      19. 7.3.19 Frequency Compensation
      20. 7.3.20 Thermal Shutdown
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Switching Frequency
        2. 8.2.2.2  Output Voltage Programming Resistor Selection
        3. 8.2.2.3  Driver PVIN Configuration
        4. 8.2.2.4  Soft-Start Capacitor Selection
        5. 8.2.2.5  Transformer Design
        6. 8.2.2.6  Primary Power Switch Selection
        7. 8.2.2.7  Output Diode Selection
        8. 8.2.2.8  RCD Clamp
        9. 8.2.2.9  Output Capacitance Selection
        10. 8.2.2.10 Current Sense Resistor
        11. 8.2.2.11 Frequency Compensation Component Selection
      3. 8.2.3 Application Curves
      4. 8.2.4 Boost Converter
      5. 8.2.5 Feedback Isolation Using ISOS510
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.18 Slope Compensation (RSC)

When utilizing peak current mode control in switching power converter design, the converter can enter into an unstable state when the duty cycle for the main power switch rises above 50%. Basically, the converter is in a state where the error between the peak current and average current increases with each subsequent switching cycle. This instability, known as subharmonic oscillation, can be mitigated by adding slope compensation. For the TPS7H502x, the slope compensation is in the form of a voltage ramp that is subtracted from the error amplifier output divided down by the parameter CCSR (COMP to CS_ILIM ratio). The minimum slope compensation for stability over the entire duty cycle range is equal to 0.5 × m, where m is the inductor falling current slope. The recommended slope compensation is 1 × m, as any increase above this value does not improve stability.

For the forward converter and boost converter, the slope compensation can be set equal to the downward slope of the output inductor current. For the flyback converter, the slope compensation is calculated using the downward slope of the current in the flyback transformer. In the isolated topologies, note that the sensed current waveform also needs to take into account the turns ratio of the transformer.

For forward:

Equation 16. SC=VOUT×RCS×ACSLOUT×NPS

For flyback:

Equation 17. SC=VOUT×RCS×ACSLPRI×NPS

For boost:

Equation 18. SC=(VOUT-VIN)×RCS×ACSL

where:

  • SC is the slope compensation value in V/μs
  • LOUT is the output inductor value in μH (forward)
  • LPRI is the primary inductance value in μH (flyback)
  • L is the inductor value in μH (boost)
  • NPS is the primary-to-secondary turns ratio
  • RCS is the value of the current sense resistor in Ω
  • ACS is the gain associated with the current sense stage, including the current sense amplifier and transformer, if used
  • VOUT is the converter output voltage
  • VIN is the converter input voltage

For the TPS7H502x controller, a resistor from the RSC pin to AGND can be used to set the desired slope compensation. Equation 19 shows the calculation for determining the proper resistor value for RSC.

Equation 19. RSC=29.5SC1.07

where:

  • SC is the desired slope compensation is V/μs
  • RSC is in kΩ