SLVSAF1E October   2010  – May 2019 TPS54388-Q1


  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Simplified Schematic
      2.      Efficiency Curve
  4. Revision History
  5. Pin Configuration and Functions
    1.     Pin Functions
  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. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Fixed-Frequency PWM Control
      2. 7.3.2 Slope Compensation and Output Current
      3. 7.3.3 Bootstrap Voltage (BOOT) and Low-Dropout Operation
      4. 7.3.4 Error Amplifier
      5. 7.3.5 Voltage Reference
    4. 7.4 Device Functional Modes
      1. 7.4.1  Adjusting the Output Voltage
      2. 7.4.2  Enable Functionality and Adjusting Undervoltage Lockout
      3. 7.4.3  Slow-Start or Tracking Pin
      4. 7.4.4  Sequencing
      5. 7.4.5  Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
      6. 7.4.6  Overcurrent Protection
      7. 7.4.7  Frequency Shift
      8. 7.4.8  Reverse Overcurrent Protection
      9. 7.4.9  Synchronize Using the RT/CLK Pin
      10. 7.4.10 Power Good (PWRGD Pin)
      11. 7.4.11 Overvoltage Transient Protection
      12. 7.4.12 Thermal Shutdown
      13. 7.4.13 Small-Signal Model for Loop Response
      14. 7.4.14 Simple Small-Signal Model for Peak-Current-Mode Control
      15. 7.4.15 Small-Signal Model for Frequency Compensation
  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.  Custom Design With WEBENCH® Tools
        2.  Selecting the Switching Frequency
        3.  Output Inductor Selection
        4.  Output Capacitor
        5.  Input Capacitor
        6.  Slow-Start Capacitor
        7.  Bootstrap Capacitor Selection
        8.  Output-Voltage and Feedback-Resistor Selection
        9.  Compensation
        10. Power-Dissipation Estimate
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Third-Party Products Disclaimer
    2. 11.2 Device Support
      1. 11.2.1 Development Support
        1. Custom Design With WEBENCH® Tools
    3. 11.3 Documentation Support
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Community Resource
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

Layout Guidelines

Layout is a critical portion of good power-supply design. The signal paths, which conduct fast-changing currents or voltages, can interact with stray inductance or parasitic capacitance in several ways to generate noise or degrade the power-supply performance. Take care to minimize the loop area formed by the bypass-capacitor connections and the VIN pins. See Figure 49 for a PCB layout example. Tie the GND pins and AGND pin directly to the thermal pad under the IC. Connect the thermal pad to any internal PCB ground planes using multiple vias directly under the IC. Use additional vias to connect the top-side ground area to any internal planes near the input and output capacitors. For operation at full-rated load, the top-side ground area, along with any additional internal ground planes, must provide adequate heat-dissipating area.

Locate the input bypass capacitor as close to the IC as possible. Route the PH pin to the output inductor. Because the PH connection is the switching node, locate the output inductor close to the PH pins, and minimize the area of the PCB conductor to prevent excessive capacitive coupling. Also. locate the boot capacitor close to the device. Connect the sensitive analog ground connections for the feedback voltage divider, compensation components, slow-start capacitor, and frequency-set resistor to a separate analog ground trace as shown. The RT/CLK pin is particularly sensitive to noise, so locate the Rt resistor as close as possible to the IC, and connect it with minimal lengths of trace. Place the additional external components approximately as shown. It may be possible to obtain acceptable performance with alternative PCB layouts. However, this layout, meant as a guideline, produces good results.