SLVSC56B September   2013  – November 2015 TPS54540-Q1

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and 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 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 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 Output Current
      3. 7.3.3  Pulse-Skip Eco-mode
      4. 7.3.4  Low Dropout Operation and Bootstrap Voltage (BOOT)
      5. 7.3.5  Error Amplifier
      6. 7.3.6  Adjusting the Output Voltage
      7. 7.3.7  Enable and Adjusting Undervoltage Lockout
      8. 7.3.8  Internal Soft Start
      9. 7.3.9  Constant Switching Frequency and Timing Resistor (RT/CLK) Pin)
      10. 7.3.10 Synchronization to RT/CLK Pin
      11. 7.3.11 Maximum Switching Frequency
      12. 7.3.12 Accurate Current Limit
      13. 7.3.13 Overvoltage Protection
      14. 7.3.14 Thermal Shutdown
      15. 7.3.15 Small Signal Model for Loop Response
      16. 7.3.16 Simple Small Signal Model for Peak Current Mode Control
      17. 7.3.17 Small Signal Model for Frequency Compensation
    4. 7.4 Device Functional Modes
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Buck Converter With 6-V to 42-V Input and 3.3-V at 5-A Output
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Selecting the Switching Frequency
          2. 8.2.1.2.2  Output Inductor Selection (LO)
          3. 8.2.1.2.3  Output Capacitor
          4. 8.2.1.2.4  Catch Diode
          5. 8.2.1.2.5  Input Capacitor
          6. 8.2.1.2.6  Bootstrap Capacitor Selection
          7. 8.2.1.2.7  Undervoltage Lockout Set Point
          8. 8.2.1.2.8  Output Voltage and Feedback Resistors Selection
          9. 8.2.1.2.9  Compensation
          10. 8.2.1.2.10 Power Dissipation Estimate
          11. 8.2.1.2.11 Safe Operating Area
          12. 8.2.1.2.12 Discontinuous Conduction Mode and Eco-mode Boundary
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Inverting Buck-Boost Topology for Positive Input to Negative Output
      3. 8.2.3 Split-Rail Power Supply
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Estimated Circuit Area
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    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

パッケージ・オプション

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メカニカル・データ(パッケージ|ピン)
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発注情報

10 Layout

10.1 Layout Guidelines

Layout is a critical portion of good power supply design. There are several signal paths that conduct fast changing currents or voltages that can interact with stray inductance or parasitic capacitance to generate noise or degrade performance. To reduce parasitic effects, the VIN pin should be bypassed to ground with a low-ESR ceramic bypass capacitor with X5R or X7R dielectric. Take care to minimize the loop area formed by the bypass capacitor connections, the VIN pin, and the anode of the catch diode. See Figure 61 for a PCB layout example. The GND pin should be tied directly to the power pad under the IC and the power pad.

The power pad must be connected to internal PCB ground planes using multiple vias directly under the IC. The SW pin should be routed to the cathode of the catch diode and to the output inductor. Because the SW connection is the switching node, the catch diode and output inductor must be located close to the SW pins, and the area of the PCB conductor minimized to prevent excessive capacitive coupling. For operation at full rated load, the top side ground area must provide adequate heat dissipating area. The RT/CLK pin is sensitive to noise so the RT resistor should be located as close as possible to the IC and routed with minimal lengths of trace. The additional external components can be placed approximately as shown. It may be possible to obtain acceptable performance with alternate PCB layouts; however, this layout has been shown to produce good results and is meant as a guideline.

10.2 Layout Example

TPS54540-Q1 layout_lvsbb4.gif Figure 61. PCB Layout Example

10.3 Estimated Circuit Area

Boxing in the components in the design of Figure 34 the estimated printed-circuit-board area is 1.025 in2
(661 mm2). This area does not include test points or connectors. If the area needs to be reduced, this can be done by using a two sided assembly and replacing the 0603 sized passives with a smaller sized equivalent.