SLUSBG4B March   2013  – August 2021 TPS53511

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
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 PWM Operation
      2. 7.3.2 PWM Frequency and Adaptive On-Time Control
      3. 7.3.3 Soft Start and Pre-Biased Soft-Start Function
      4. 7.3.4 Power Good
      5. 7.3.5 Output Discharge Control
      6. 7.3.6 Current Protection
      7. 7.3.7 Overvoltage/Undervoltage Protection
      8. 7.3.8 UVLO Protection
      9. 7.3.9 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Light Load Mode Control
  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 Output Inductor Selection
        2. 8.2.2.2 Output Capacitor Selection
        3. 8.2.2.3 Input Capacitor Selection
        4. 8.2.2.4 Bootstrap Capacitor Selection
        5. 8.2.2.5 VREG5 Capacitor Selection
        6. 8.2.2.6 Output Voltage Setting Resistors Selection
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Considerations
      1. 10.1.1 Thermal Information
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support 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

8.2.2.1 Output Inductor Selection

The value of the output filtering inductor determines the magnitude of the current ripple, which also affects the output voltage ripple for a certain output capacitance value. Increasing the inductance value reduces the ripple current, and thus, results in reduced conduction loss and output ripple voltage. Alternatively, low inductance value is needed due to the demand of low profile and fast transient response. Therefore, it is important to obtain a compromise between the low ripple current and low inductance value.

In practical application, the peak-to-peak current ripple is usually designed to be between 1/4 to1/2 of the rated load current. Since the magnitude of the current ripple is determined by inductance value, switching frequency, input voltage and output voltage, the required inductance value for a certain required ripple ∆I is shown in Equation 3. Also, the chosen inductor should be rated for the peak current calculated from Equation 4.

Equation 3. GUID-90946FCF-D678-4770-9E5A-95C7E314AFC5-low.gif
Equation 4. GUID-38461EB4-A69F-4C53-B0B4-FDEF4C17E9A0-low.gif

where

  • VIN is the input voltage.
  • VOUT is the output voltage.
  • IRIPPLE is the required current ripple.
  • ƒSW is the switching frequency.

For this design example, the inductance value is selected to provide approximately 30% peak-to-peak ripple current at maximum load. For this design, a nearest standard value was chosen: 3.3 µH. For 3.3 µH, the calculated peak current is 1.71 A.