SNVSBT8 March   2021 TPSM13604H

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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
  7. 7 Detailed Description
    1. 7.1 Overview
      1. 7.1.1 COT Control Circuit Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Output Overvoltage Comparator
      2. 7.3.2 Current Limit
      3. 7.3.3 Thermal Protection
      4. 7.3.4 Zero Coil Current Detection
      5. 7.3.5 Prebiased Start-up
    4. 7.4 Device Functional Modes
      1. 7.4.1 Discontinuous Conduction and Continuous Conduction Modes
  8. 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 Design Steps for the TPSM13604 Application
          1. 8.2.2.1.1 Enable Divider, RENT, and RENB Selection
          2. 8.2.2.1.2 Output Voltage Selection
          3. 8.2.2.1.3 Soft-Start Capacitor, CSS, Selection
          4. 8.2.2.1.4 Output Capacitor, CO, Selection
            1. 8.2.2.1.4.1 Capacitance
            2. 8.2.2.1.4.2 ESR
          5. 8.2.2.1.5 Input Capacitor, CIN, Selection
          6. 8.2.2.1.6 ON-Time, RON, Resistor Selection
            1. 8.2.2.1.6.1 Discontinuous Conduction and Continuous Conduction Mode Selection
      3. 8.2.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Power Module SMT Guidelines
    2. 10.2 Layout Example
      1. 10.2.1 Power Dissipation and Board Thermal Requirements
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Glossary
    7. 11.7 Electrostatic Discharge Caution
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information
8.2.2.1.3 Soft-Start Capacitor, CSS, Selection

Programmable soft start permits the regulator to slowly ramp to its steady-state operating point after being enabled, thereby reducing current inrush from the input supply and slowing the output voltage rise-time to prevent overshoot.

Upon turn-on, after all UVLO conditions have been passed, an internal 8-µA current source begins charging the external soft-start capacitor. The soft-start time duration to reach steady-state operation is given by the formula:

Equation 4. tSS = VREF × CSS / Iss = 0.8 V × CSS / 8 µA

Equation 4 can be rearranged as follows:

Equation 5. CSS = tSS × 8 μA / 0.8 V

Use of a 4700-pF capacitor results in 0.5-ms soft-start duration. This is a recommended value. Note high values of CSS capacitance causes more output voltage droop when a load transient goes across the DCM-CCM boundary. Use Equation 22 to find the DCM-CCM boundary load current for the specific operating condition. If a fast load transient response is desired for steps between DCM and CCM mode, the soft-start capacitor value must be less than 0.018 µF.

Note the following conditions reset the soft-start capacitor by discharging the SS input to ground with an internal 200-μA current sink:

  • The enable input being pulled low
  • Thermal shutdown condition
  • Overcurrent fault
  • Internal VINUVLO