SLVS757E March   2007  – July 2022 TPS5450

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  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  Oscillator Frequency
      2. 7.3.2  Voltage Reference
      3. 7.3.3  Enable (ENA) and Internal Slow-Start
      4. 7.3.4  Undervoltage Lockout (UVLO)
      5. 7.3.5  Boost Capacitor (BOOT)
      6. 7.3.6  Output Feedback (VSENSE) and Internal Compensation
      7. 7.3.7  Voltage Feed-Forward
      8. 7.3.8  Pulse-Width-Modulation (PWM) Control
      9. 7.3.9  Overcurrent Limiting
      10. 7.3.10 Overvoltage Protection
      11. 7.3.11 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation near Minimum Input Voltage
      2. 7.4.2 Operation With ENA 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 Switching Frequency
        2. 8.2.2.2 Output Voltage Setpoint
        3. 8.2.2.3 Input Capacitors
        4. 8.2.2.4 Output Filter Components
        5. 8.2.2.5 Inductor Selection
        6. 8.2.2.6 Capacitor Selection
        7.       43
        8. 8.2.2.7 Boot Capacitor
        9. 8.2.2.8 Catch Diode
        10. 8.2.2.9 Advanced Information
          1. 8.2.2.9.1 Output Voltage Limitations
          2. 8.2.2.9.2 Internal Compensation Network
      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 Calculations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • DDA|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.2.6 Capacitor Selection

The important design factors for the output capacitor are DC voltage rating, ripple current rating, and equivalent series resistance (ESR). The DC voltage and ripple current ratings cannot be exceeded. The ESR is important because along with the inductor ripple current it determines the amount of output ripple voltage. The actual value of the output capacitor is not critical, but some practical limits do exist. Consider the relationship between the desired closed-loop crossover frequency of the design and LC corner frequency of the output filter. Due to the design of the internal compensation, it is desirable to keep the closed-loop crossover frequency in the range 3 kHz to 30 kHz as this frequency range has adequate phase boost to allow for stable operation. For this design example, it is assumed that the intended closed-loop crossover frequency will be between 2590 Hz and 24 kHz and also below the ESR zero of the output capacitor. Under these conditions the closed-loop crossover frequency is related to the LC corner frequency by:

Equation 8. GUID-F05416C4-D189-441C-A9F1-47244C4F68A5-low.gif

And the desired output capacitor value for the output filter to:

Equation 9. GUID-938D9F7F-6D1D-410A-9CE8-B1BD75C7A058-low.gif

For a desired crossover of 12 kHz and a 15-μH inductor, the calculated value for the output capacitor is 330 μF. The capacitor type should be chosen so that the ESR zero is above the loop crossover. The maximum ESR should be:

Equation 10. GUID-B37F545F-45C1-4575-9C72-32001823905A-low.gif