SNVSB92 December   2018 TPS54340B

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
      2.      Efficiency vs Load 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 Timing Requirements
    7. 6.7 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  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 Accurate Current Limit Operation and Maximum Switching Frequency
      11. 7.3.11 Synchronization to RT/CLK pin
      12. 7.3.12 Overvoltage Protection
      13. 7.3.13 Thermal Shutdown
      14. 7.3.14 Small Signal Model for Loop Response
      15. 7.3.15 Simple Small Signal Model for Peak-Current-Mode Control
      16. 7.3.16 Small Signal Model for Frequency Compensation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation with VIN ≤ 4.5 V (Minimum VIN)
      2. 7.4.2 Operation with EN Control
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application: Buck Converter
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedures
        1. 8.2.2.1  Custom Design with WEBENCH® Tools
        2. 8.2.2.2  Selecting the Switching Frequency
        3. 8.2.2.3  Output Inductor Selection (LO)
        4. 8.2.2.4  Output Capacitor
        5. 8.2.2.5  Catch Diode
        6. 8.2.2.6  Input Capacitor
        7. 8.2.2.7  Bootstrap Capacitor Selection
        8. 8.2.2.8  Undervoltage Lockout Setpoint
        9. 8.2.2.9  Output Voltage and Feedback Resistors Selection
        10. 8.2.2.10 Minimum VIN
        11. 8.2.2.11 Compensation
        12. 8.2.2.12 Discontinuous Conduction Mode and Eco-mode Boundary
        13. 8.2.2.13 Power Dissipation
      3. 8.2.3 Application Curves
    3. 8.3 Other Applications
      1. 8.3.1 Inverting Power
      2. 8.3.2 Split-Rail Power Supply
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
      1. 10.2.1 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 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
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.14 Small Signal Model for Loop Response

Figure 28 shows an equivalent model for the TPS54340B control loop which can be simulated to check the frequency response and dynamic load response. The error amplifier is a transconductance amplifier with a gmEA of 350 μA/V. The error amplifier can be modeled using an ideal voltage controlled current source. The resistor Ro and capacitor Co model the open loop gain and frequency response of the amplifier. The 1-mV AC voltage source between the nodes a and b effectively breaks the control loop for the frequency response measurements. Plotting c/a provides the small signal response of the frequency compensation. Plotting a/b provides the small signal response of the overall loop. The dynamic loop response can be evaluated by replacing RL with a current source with the appropriate load step amplitude and step rate in a time domain analysis. This equivalent model is only valid for continuous conduction mode (CCM) operation.

TPS54340B ss_loop_res_lvsbb4.gifFigure 28. Small Signal Model for Loop Response