SLVSII7 December   2025 TPSM8D7420 , TPSM8D7620

PRODUCTION DATA  

  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 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 Range (VIN)
      2. 7.3.2  Bias Supply Regulator (VCC)
      3. 7.3.3  Device Configuration Pin (MSEL)
      4. 7.3.4  Multiphase Output Configuration
      5. 7.3.5  Enable and Adjustable UVLO
      6. 7.3.6  Adjustable Switching Frequency
      7. 7.3.7  Device Synchronization (SYNC)
        1. 7.3.7.1 Clock Locking
      8. 7.3.8  Adjustable Output Voltage (FB)
      9. 7.3.9  Control Loop Compensation (COMP)
      10. 7.3.10 Slope Compensation
      11. 7.3.11 Power-Good Output Voltage Monitoring
      12. 7.3.12 Output Discharge
      13. 7.3.13 Soft-Start (SS)
      14. 7.3.14 Overcurrent Protection (OCP)
      15. 7.3.15 Temperature Output
      16. 7.3.16 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Standby Mode
      3. 7.4.3 Active Mode
        1. 7.4.3.1 Peak Current Mode Operation
        2. 7.4.3.2 Diode Emulation
        3. 7.4.3.3 FPWM Mode Operation
        4. 7.4.3.4 Minimum On-time (High Input Voltage) Operation
        5. 7.4.3.5 Dropout
        6. 7.4.3.6 Recovery from Dropout
  9. 8 Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Choosing the Switching Frequency
        3. 8.2.2.3 Setting the Output Voltage
        4. 8.2.2.4 Integrated Inductor Considerations
        5. 8.2.2.5 Input Capacitor Selection
        6. 8.2.2.6 VCC and BOOT Capacitors
        7. 8.2.2.7 Output Capacitor Selection
        8. 8.2.2.8 Compensation Selection
      3. 8.2.3 Application Curves
    3. 8.3 2-PH Application
      1. 8.3.1 Design Requirements
      2. 8.3.2 Detailed Design Procedure
      3. 8.3.3 Application Curves 2-PH
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
        1. 8.5.1.1 Thermal Design and Layout
      2. 8.5.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
      2. 9.1.2 Development Support
        1. 9.1.2.1 Custom Design With WEBENCH® Tools
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.13 Soft-Start (SS)

To prevent inrush current when VOUT is enabled, the TPSM8D7x20 uses an adjustable soft-start pin to slowly ramp the reference voltage. The soft-start feature limits in-rush current on start-up and facilitates a smooth ramp up of VOUT. Soft start is triggered by any of the following conditions:

  • EN is used to turn on the device.
  • Recovery from a hiccup waiting period
  • Recovery from shutdown due to overtemperature protection.
  • Power is applied to the VIN of the IC or the VCC UVLO is released.
After soft start is triggered, the IC takes the following actions:
  • The reference used by the IC to regulate output voltage is slowly ramped from zero. The net result is that output voltage, if previously 0V, takes tSS to reach 90% of the target value.
  • Operating mode is set to diode emulation. This allows start-up without pulling output low if there is a voltage already present on the output.
  • Hiccup is disabled for the duration of soft start

This operation allows the use of output capacitors and loading conditions that cause current to border on current limit during start-up without triggering hiccup. In addition, if output voltage is prebiased, the output is not pulled down.

The following equation can be used to calculate the soft-start capacitor value CSS based on the desired soft-start time tSS.

Equation 7. CSS=tSS×ISS(R)VFB

The soft-start charge current ISS(R) and the nominal reference voltage VFB can be found in the Electrical Characteristics.