SLVSBX8B May   2013  – January 2019 TPS55330

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application (Boost)
      2.      Efficiency vs Output Current
  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 Operation
      2. 7.3.2 Switching Frequency
      3. 7.3.3 Overcurrent Protection and Frequency Foldback
        1. 7.3.3.1 Minimum On-Time and Pulse Skipping
      4. 7.3.4 Voltage Reference and Setting Output Voltage
      5. 7.3.5 Soft-Start
      6. 7.3.6 Slope Compensation
      7. 7.3.7 Enable and Thermal Shutdown
      8. 7.3.8 Undervoltage Lockout (UVLO)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation With VI < 2.9 V (Minimum VI)
      2. 7.4.2 Operation With EN Control
      3. 7.4.3 Operation at Light Loads
  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  Custom Design With WEBENCH® Tools
        2. 8.2.2.2  Selecting the Switching Frequency (R4)
        3. 8.2.2.3  Determining the Duty Cycle
        4. 8.2.2.4  Selecting the Inductor (L1)
        5. 8.2.2.5  Computing the Maximum Output Current
        6. 8.2.2.6  Selecting the Output Capacitor (C8-C10)
        7. 8.2.2.7  Selecting the Input Capacitors (C2, C7)
        8. 8.2.2.8  Setting Output Voltage (R1, R2)
        9. 8.2.2.9  Setting the Soft-start Time (C7)
        10. 8.2.2.10 Selecting the Schottky Diode (D1)
        11. 8.2.2.11 Compensating the Control Loop (R3, C4, C5)
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design With WEBENCH® Tools
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.5 Computing the Maximum Output Current

The over-current limit for the integrated power MOSFET limits the maximum input current and thus the maximum input power for a given input voltage. Maximum output power is less than maximum input power due to power conversion losses. Therefore, the current limit setting, input voltage, output voltage and efficiency can all change maximum current output (IOUTmax). The current limit clamps the peak inductor current, therefore the ripple has to be subtracted to derive maximum DC current. Decreasing the KIND or designing for a higher efficiency will increase the maximum output current. This can be evaluated with the chosen inductance or the chosen KIND. This should be evaluated with the minimum input voltage and minimum peak current limit (ILIM) of 5.25 A.

Equation 17. TPS55330 eq17_Ioutmax_lvsbx8.gif

In this design with 2.9 V input boosted to 5 V output and a 2.2 μH inductor with an assumed the Schottky forward voltage of 0.5 V and estimated efficiency of 80%, the maximum output current is 2.25 A. With the 4.2 V input and increased estimated efficiency of 90%, the maximum output current increases to 3.68 A.