SBVS311A November   2019  – March 2020 TPS7A54

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
    1.     Powering Digital Loads
  3. 3 Description
    1.     Powering RF Components
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Voltage Regulation Features
        1. 7.3.1.1 DC Regulation
        2. 7.3.1.2 AC and Transient Response
      2. 7.3.2 System Start-Up Features
        1. 7.3.2.1 Programmable Soft Start (NR/SS Pin)
        2. 7.3.2.2 Internal Sequencing
          1. 7.3.2.2.1 Enable (EN)
          2. 7.3.2.2.2 Undervoltage Lockout (UVLO) Control
          3. 7.3.2.2.3 Active Discharge
        3. 7.3.2.3 Power-Good Output (PG)
      3. 7.3.3 Internal Protection Features
        1. 7.3.3.1 Foldback Current Limit (ICL)
        2. 7.3.3.2 Thermal Protection (Tsd)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Regulation
      2. 7.4.2 Disabled
      3. 7.4.3 Current Limit Operation
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1  Recommended Capacitor Types
        1. 8.1.1.1 Input and Output Capacitor Requirements (CIN and COUT)
        2. 8.1.1.2 Noise-Reduction and Soft-Start Capacitor (CNR/SS)
        3. 8.1.1.3 Feed-Forward Capacitor (CFF)
      2. 8.1.2  Soft Start and Inrush Current
      3. 8.1.3  Optimizing Noise and PSRR
      4. 8.1.4  Charge Pump Noise
      5. 8.1.5  Current Sharing
      6. 8.1.6  Adjustable Operation
      7. 8.1.7  Power-Good Operation
      8. 8.1.8  Undervoltage Lockout (UVLO) Operation
      9. 8.1.9  Dropout Voltage (VDO)
      10. 8.1.10 Device Behavior During Transition From Dropout Into Regulation
      11. 8.1.11 Load Transient Response
      12. 8.1.12 Reverse Current Protection Considerations
      13. 8.1.13 Power Dissipation (PD)
      14. 8.1.14 Estimating Junction Temperature
      15. 8.1.15 TPS7A54EVM Thermal Analysis
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Board Layout
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Evaluation Modules
        2. 11.1.1.2 Spice Models
      2. 11.1.2 Device Nomenclature
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community 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

8.1.2 Soft Start and Inrush Current

Soft start refers to the ramp-up characteristic of the output voltage during LDO turnon after EN and UVLO achieve threshold voltage. The noise-reduction capacitor serves a dual purpose of both governing output noise reduction and programming the soft-start ramp during turnon.

Inrush current is defined as the current into the LDO at the IN pin during start-up. Inrush current then consists primarily of the sum of load current and the current used to charge the output capacitor. This current is difficult to measure because the input capacitor must be removed, which is not recommended. However, Equation 3 can estimate this soft-start current:

Equation 3. TPS7A54 q_iout-t_bvs204.gif

where

  • VOUT(t) is the instantaneous output voltage of the turnon ramp
  • dVOUT(t) / dt is the slope of the VOUT ramp
  • RLOAD is the resistive load impedance