SLUSEF1D September   2021  – November 2024 TPSM82864A , TPSM82866A

PRODMIX  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Options
  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 Power Save Mode
      2. 7.3.2 Forced PWM Mode
      3. 7.3.3 Optimized Transient Performance from PWM to PSM Operation
      4. 7.3.4 Low Dropout Operation (100% Duty Cycle)
      5. 7.3.5 Soft Start
      6. 7.3.6 Switch Current Limit and HICCUP Short-Circuit Protection
      7. 7.3.7 Undervoltage Lockout
      8. 7.3.8 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Enable and Disable (EN)
      2. 7.4.2 Output Discharge
      3. 7.4.3 Power Good (PG)
      4. 7.4.4 Output Voltage and Mode Selection (VSET/MODE)
  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 Setting The Output Voltage
        2. 8.2.2.2 Input and Output Capacitor Selection
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Examples
        1. 8.4.2.1 Thermal Considerations
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
    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

7.3.5 Soft Start

After enabling the device, there is a 650-µs enable delay (tDelay) before the device starts switching. The tDelay time varies with the VSET/MODE resistor used and is longest with a resistance of 249 kΩ or higher. After the enable delay, an internal soft-start circuit ramps up the output voltage in 1 ms (tRamp). This action avoids excessive inrush current and creates a smooth output voltage ramp up. This action also prevents excessive voltage drops of batteries that have a high internal impedance. Figure 7-2 shows the start-up sequence.

TPSM82864A TPSM82866A Start-Up SequenceFigure 7-2 Start-Up Sequence

The device is able to start into a prebiased output capacitor. The device starts with the applied bias voltage and ramps the output voltage to the nominal value.