SLVSB10F July   2012  – November 2020 TPS54020

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (Continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings (1)
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Fixed Frequency PWM Control
      2. 8.3.2  Input Voltage and Power Input Voltage Pins (VIN and PVIN)
      3. 8.3.3  Voltage Reference (VREF)
      4. 8.3.4  Adjusting the Output Voltage
      5. 8.3.5  Safe Start-up into Prebiased Outputs
      6. 8.3.6  Error Amplifier
      7. 8.3.7  Slope Compensation
      8. 8.3.8  Enable and Adjusting Undervoltage Lockout
      9. 8.3.9  Adjustable Switching Frequency and Synchronization (RT/CLK)
      10. 8.3.10 Soft-Start (SS) Sequence
      11. 8.3.11 Power Good (PWRGD)
      12. 8.3.12 Bootstrap Voltage (BOOT) and Low Dropout Operation
      13. 8.3.13 Sequencing (SS)
      14. 8.3.14 Output Overvoltage Protection (OVP)
      15. 8.3.15 Overcurrent Protection
        1. 8.3.15.1 High-side MOSFET Overcurrent Protection
        2. 8.3.15.2 Low-side MOSFET Overcurrent Protection
      16. 8.3.16 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Single-Supply Operation
      2. 8.4.2 Split Rail Operation
      3. 8.4.3 Continuous Current Mode Operation (CCM)
      4. 8.4.4 Eco-mode Light-Load Efficiency Operation
      5. 8.4.5 Adjustable Switching Frequency (RT Mode)
      6. 8.4.6 Synchronization (CLK Mode)
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Small Signal Model for Loop Response
      2. 9.1.2 Simple Small Signal Model for Peak Current Mode Control
      3. 9.1.3 Small Signal Model for Frequency Compensation
      4. 9.1.4 Designing the Device Loop Compensation
        1. 9.1.4.1 Step One: Determine the Crossover Frequency (fC)
        2. 9.1.4.2 Step Two: Determine a Value for R6
        3. 9.1.4.3 Step Three: Calculate the Compensation Zero.
        4. 9.1.4.4 Step Four: Calculate the Compensation Noise Pole.
        5. 9.1.4.5 Step Five: Calculate the Compensation Phase Boost Zero.
      5. 9.1.5 Fast Transient Considerations
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1  Custom Design With WEBENCH® Tools
        2. 9.2.2.2  Operating Frequency
        3. 9.2.2.3  Output Inductor Selection
        4. 9.2.2.4  Output Capacitor Selection
          1. 9.2.2.4.1 Response to a Load Transient
          2. 9.2.2.4.2 Output Voltage Ripple
          3. 9.2.2.4.3 Bus Capacitance
        5. 9.2.2.5  Input Capacitor Selection
        6. 9.2.2.6  Soft-Start Capacitor Selection
        7. 9.2.2.7  Bootstrap Capacitor Selection
        8. 9.2.2.8  Undervoltage Lockout Set Point
        9. 9.2.2.9  Output Voltage Feedback Resistor Selection
          1. 9.2.2.9.1 Minimum Output Voltage
        10. 9.2.2.10 Compensation Component Selection
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Examples
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
        1. 12.1.1.1 Custom Design With WEBENCH® Tools
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.8 Enable and Adjusting Undervoltage Lockout

The EN pin provides electrical on and off control of the device. Once the EN pin voltage exceeds the threshold voltage, the device starts operation. If the EN pin voltage is pulled below the threshold voltage, the regulator stops switching and enters low quiescent state. The EN pin has an internal hysteretic current source, allowing the user to design the ON and OFF threshold voltages with a resistor divider at the EN pin. If an application requires controlling the EN pin, use open drain or open collector output logic to interface with the pin.

The EN pin can be configured as shown in Figure 8-1, Figure 8-2, and Figure 8-3. It is recommended to set the UVLO hysteresis to be greater than 500 mV to avoid repeated chatter during start-up or shutdown. The EN pin has a small fixed pullup current iP which sets the current source value before the start-up sequence. The device includes the second current source iH when the threshold voltage has been exceeded. To achieve clean transitions between the OFF and ON states, TI recommendeds that the turn OFF threshold is no less than 4.2 V, and the turn ON threshold is no less than 4.4 V on the VIN pin.

The UVLO thresholds can be calculated using Equation 2 and Equation 3.

GUID-FDC06D01-9E5B-47F9-87E3-158AF2A67E9A-low.gifFigure 8-1 Adjustable VIN Undervoltage Lockout
GUID-91C1AC6E-93D5-4EEF-9E3C-5B85B01559B1-low.gifFigure 8-3 Adjustable VIN and PVIN Undervoltage Lockout
GUID-6885BA9E-34E9-48F7-B002-AFB8D288C212-low.gifFigure 8-2 Adjustable PVIN Undervoltage Lockout, PVIN ≥ 4.5 V

R3, the top UVLO divider resistor, is calculated using Equation 2.

Equation 2. GUID-68EC5941-4B2D-4AD9-9C71-B7FC5EB78622-low.gif

R5, the bottom UVLO divider resistor, is calculated in Equation 3.

Equation 3. GUID-B34B456B-4F05-4834-AF88-7A07F559B419-low.gif

In this example:

  • IH = 3.3 μA
  • IP = 1.15 μA
  • VENRISING = 1.22 V
  • VENFALLING = 1.17 V