SNVSBF6B October   2019  – December 2020 TPSM265R1

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 (VIN = 5 V)
    7. 6.7  Typical Characteristics (VIN = 12 V)
    8. 6.8  Typical Characteristics (VIN = 24 V)
    9. 6.9  Typical Characteristics (VIN = 48 V)
    10. 6.10 Typical Characteristics (VIN = 65 V)
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Adjustable Output Voltage (FB)
      2. 7.3.2 Input Capacitor Selection
      3. 7.3.3 Output Capacitor Selection
      4. 7.3.4 Precision Enable (EN), Undervoltage Lockout (UVLO), and Hysteresis (HYS)
      5. 7.3.5 PFM Operation
      6. 7.3.6 Power Good (PGOOD)
      7. 7.3.7 Configurable Soft Start (SS)
        1. 7.3.7.1 Prebiased Start-up
      8. 7.3.8 Overcurrent Protection (OCP)
      9. 7.3.9 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
      4. 7.4.4 Sleep Mode
  8. 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 Output Voltage Setpoint
        3. 8.2.2.3 Input Capacitors
        4. 8.2.2.4 Output Capacitor Selection
        5. 8.2.2.5 UVLO Programming
        6. 8.2.2.6 Soft-Start Capacitor – CSS
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
      1. 10.2.1 Theta JA versus PCB Area
      2. 10.2.2 Package Specifications
      3. 10.2.3 EMI
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
      3. 11.1.3 Custom Design With WEBENCH® Tools
    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 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.7 Configurable Soft Start (SS)

The TPSM265R1 has a flexible and easy-to-use soft-start control pin, SS. The soft-start feature prevents inrush current when power is first applied. Soft start is achieved by slowly ramping up the target regulation voltage when the device is powered up or enabled. Selectable and adjustable start-up timing options include minimum delay (no soft start), 900-µs internally fixed soft start, and an externally programmable soft start.

Leaving the SS pin open enables the internal soft-start control ramp with a soft-start interval of 900 µs. The soft-start time can be increased by connecting an external capacitor, CSS, from SS to GND. Applications with a large amount of output capacitance or higher output voltage can benefit from increasing the soft-start time. Longer soft-start time reduces the supply current needed to charge the output capacitors and supply any output loading. An internal current source, ISS, of 10 µA charges CSS and generates a ramp to control the ramp rate of the output voltage. Use Equation 4 to calculate the CSS capacitance for a desired soft-start time, tSS.

Equation 4. GUID-BF399CB2-FA86-40D2-B906-15D46DBA8754-low.gif

CSS is discharged by an internal FET when VOUT is shut down by EN, UVLO, or thermal shutdown.

It is desirable in some applications for the output voltage to reach its nominal setpoint in the shortest possible time. Connecting a 100-kΩ resistor from SS to GND disables the soft-start circuit, and the TPSM265R1 operates in current limit during start-up to rapidly charge the output capacitance.