SLVSGM1C July   2023  – April 2025 TPSM828301 , TPSM828302 , TPSM828303

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 RDS Package
    5. 6.5 Thermal Information VCB Package
    6. 6.6 Electrical Characteristics
    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 Pulse Width Modulation (PWM) Operation
      2. 7.3.2 Power Save Mode (PSM) Operation
      3. 7.3.3 Start-Up and Soft Start
      4. 7.3.4 Switch Cycle-by-Cycle Current Limit
      5. 7.3.5 Undervoltage Lockout
      6. 7.3.6 Thermal Shutdown
      7. 7.3.7 Optimized EMI Performance
      8. 7.3.8 VOUT Accuracy
    4. 7.4 Device Functional Modes
      1. 7.4.1 Enable, Disable, and Output Discharge
      2. 7.4.2 Minimum Duty Cycle and 100% Mode Operation
      3. 7.4.3 Power Good
  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 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Setting The Output Voltage
        3. 8.2.2.3 Input Capacitor Selection
        4. 8.2.2.4 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 Example
        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. 9.1.2 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 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
    1. 11.1 Tape and Reel Information

7.3.3 Start-Up and Soft Start

When the EN voltage goes High, the device starts loading the default values into the device registers. This action is done within td(EN). After that, the internal soft-start circuitry controls the output voltage during start-up. This control avoids excessive inrush current and makes sure of a controlled output voltage ramp. This control also prevents unwanted voltage drops from high-impedance power sources or batteries. Finally, the PG signal has a delay td(PG) at start-up. Figure 7-3 shows a start-up sequence, where the EN pin is pulled up to VIN.

TPSM828301 TPSM828302 TPSM828303 Start-Up Timing When EN is Pulled Up to VIN Figure 7-3 Start-Up Timing When EN is Pulled Up to VIN

Figure 7-4 shows a start-up sequence, where an external signal is connected to the EN pin. The soft start function has a second purpose. During start-up the output capacitor needs to charge. Larger output voltage combined with large output capacitance can trigger an over current event and prevent the device from starting up correctly. The circuit designer needs to select the maximum output capacitance in accordance to the target output voltage and start-up time. The TPSM82830xK version can mitigate the peak output current with a longer start-up time.

TPSM828301 TPSM828302 TPSM828303 Start-Up Timing When an External Signal is Connected to the EN Pin Figure 7-4 Start-Up Timing When an External Signal is Connected to the EN Pin

The TPSM82830x can start into a prebiased output if enabled for the first time. For a new prebiased operation, a power cycle is needed to disable the active output discharge. Figure 7-5 shows a start-up into a prebiased output voltage.

TPSM828301 TPSM828302 TPSM828303 Start-Up into a Prebiased Output Figure 7-5 Start-Up into a Prebiased Output