SLVSBK0D October   2012  – March 2017 TPS54340

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) Terminal)
      10. 7.3.10 Accurate Current Limit Operation and Maximum Switching Frequency
      11. 7.3.11 Synchronization to RT/CLKTerminal
      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 Applications
      1. 8.2.1 Buck Converter
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedures
          1. 8.2.1.2.1  Custom Design with WEBENCH Tools
          2. 8.2.1.2.2  Selecting the Switching Frequency
          3. 8.2.1.2.3  Output Inductor Selection (LO)
          4. 8.2.1.2.4  Output Capacitor
          5. 8.2.1.2.5  Catch Diode
          6. 8.2.1.2.6  Input Capacitor
          7. 8.2.1.2.7  Bootstrap Capacitor Selection
          8. 8.2.1.2.8  Undervoltage Lockout Set Point
          9. 8.2.1.2.9  Output Voltage and Feedback Resistors Selection
          10. 8.2.1.2.10 Minimum VIN
          11. 8.2.1.2.11 Compensation
          12. 8.2.1.2.12 Discontinuous Conduction Mode and Eco-mode Boundary
          13. 8.2.1.2.13 Power Dissipation
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Inverting Power
      3. 8.2.3 Split Rail Power Supply
    3. 8.3 WEBENCH Power Designer
  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 Custom Design with WEBENCH Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Receiving Notification of Documentation Updates
      2. 11.2.2 Related Documentation
    3. 11.3 Trademarks
    4. 11.4 Community Resources
    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

8.2.1.2.8 Undervoltage Lockout Set Point

The Undervoltage Lockout (UVLO) can be adjusted using an external voltage divider on the EN terminal of the TPS54340. The UVLO has two thresholds, one for power up when the input voltage is rising and one for power down or brown outs when the input voltage is falling. For the example design, the supply should turn on and start switching once the input voltage increases above 5.75 V (UVLO start). After the regulator starts switching, it should continue to do so until the input voltage falls below 4.5 V (UVLO stop).

Programmable UVLO threshold voltages are set using the resistor divider of RUVLO1 and RUVLO2 between Vin and ground connected to the EN terminal. Equation 4 and Equation 5 calculate the resistance values necessary. For the example application, a 365 kΩ between Vin and EN (RUVLO1) and a 86.6 kΩ between EN and ground (RUVLO2) are required to produce the 8 V and 6.25 V start and stop voltages.

Equation 40. TPS54340 q_R1_lvsBK0.gif
Equation 41. TPS54340 q_R2_lvsBK0.gif