SLUSF03 august   2023 TPS51385

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  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  PWM Operation and D-CAP3™ Control Mode
      2. 7.3.2  VCC LDO
      3. 7.3.3  Soft Start
      4. 7.3.4  Enable Control
      5. 7.3.5  Power Good
      6. 7.3.6  Overcurrent Protection and Undervoltage Protection
      7. 7.3.7  UVLO Protection
      8. 7.3.8  Overvoltage Protection
      9. 7.3.9  Output Voltage Discharge
      10. 7.3.10 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 MODE Pin
      2. 7.4.2 Out-of-Audio™ Mode
      3. 7.4.3 Power Save Mode (PSM)
  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 External Component Selection
          1. 8.2.2.1.1 Inductor Selection
          2. 8.2.2.1.2 Output Capacitor Selection
          3. 8.2.2.1.3 Input 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
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
    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. 10Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.3 Soft Start

The TPS51385 has an internal 1-ms soft start, and also an external SS pin is provided for setting higher soft-start time if needed. When the EN pin becomes high, the soft-start function begins ramping up the reference voltage to the PWM comparator.

If the application needs a larger soft-start time, this soft-start time can be set by connecting a capacitor on SS pin. When the EN pin becomes high, the soft-start charge current (ISS) begins charging the external capacitor (CSS) connected between SS and AGND. The devices tracks the lower of the internal soft-start voltage or the external soft-start voltage as the reference. The equation for the soft-start time (TSS) is shown in the following equation:

Equation 2. TSS=CSS(nF)×VREF(V)×1.4ISS(μA)

where

  • Vref is 0.6 V and ISS is 5 μA
  • 1.4 is typical value of correlation factor