SLVSGP3A May   2023  – February 2024 TPS54KB20

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  Internal VCC LDO and Using External Bias On the VCC Pin
      2. 6.3.2  Enable
      3. 6.3.3  Adjustable Soft Start
      4. 6.3.4  Power Good
      5. 6.3.5  Output Voltage Setting
      6. 6.3.6  Remote Sense
      7. 6.3.7  D-CAP4 Control
      8. 6.3.8  Multifunction Select (MSEL) Pin
      9. 6.3.9  Low-side MOSFET Zero-Crossing
      10. 6.3.10 Current Sense and Positive Overcurrent Protection
      11. 6.3.11 Low-side MOSFET Negative Current Limit
      12. 6.3.12 Overvoltage and Undervoltage Protection
      13. 6.3.13 Output Voltage Discharge
      14. 6.3.14 UVLO Protection
      15. 6.3.15 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Auto-Skip Eco-mode Light Load Operation
      2. 6.4.2 Forced Continuous-Conduction Mode
      3. 6.4.3 Powering the Device From a Single Bus
      4. 6.4.4 Powering the Device From a Split-rail Configuration
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1  Output Voltage Setting Point
        2. 7.2.2.2  Choose the Switching Frequency and the Operation Mode
        3. 7.2.2.3  Choose the Inductor
        4. 7.2.2.4  Set the Current Limit (ILIM)
        5. 7.2.2.5  Choose the Output Capacitor
        6. 7.2.2.6  RAMP Selection
        7. 7.2.2.7  Choose the Input Capacitors (CIN)
        8. 7.2.2.8  Soft-Start Capacitor (SS Pin)
        9. 7.2.2.9  EN Pin Resistor Divider
        10. 7.2.2.10 VCC Bypass Capacitor
        11. 7.2.2.11 BOOT Capacitor
        12. 7.2.2.12 RC Snubber
        13. 7.2.2.13 PG Pullup Resistor
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

7.2.2.9 EN Pin Resistor Divider

A resistor divider on the EN pin can be used to increase the input voltage the converter begins the start-up sequence. To set the start voltage, first select the bottom resistor (REN_B). The recommended value is between 1kΩ and 100kΩ. There is an internal pulldown resistance with a nominal value of 1MΩ and this internal pulldown resistance must be included for the most accurate calculations. This requirement is especially important when the bottom resistor is a higher value, near 100kΩ. This example uses a 100kΩ resistor, and this resistor combined with the internal resistance in parallel results in an equivalent bottom resistance of 90.9kΩ. The top resistor value for the target start voltage is calculated with Equation 36. In this example, the nearest standard value of 200kΩ is selected for REN_T. When selecting a start voltage in a wide input range application, be cautious that the EN pin absolute maximum voltage of 7V is not exceeded.

Equation 36. R E N _ T = R E N _ B × V S T A R T V E N H - R E N B = 90.9   k Ω × 3.8   V 1.2   V - 90.9   k Ω = 197   k Ω

The start and stop voltages with the selected EN resistor divider can be calculated with Equation 37 and Equation 38.

Equation 37. V S T A R T = V E N H × R E N _ B + R E N _ T R E N _ B = 1.2   V × 90.9   k Ω + 200   k Ω 90.9   k Ω = 3.8   V
Equation 38. V S T O P = V E N L × R E N _ B + R E N _ T R E N _ B = 1   V × 90.9   k Ω + 200   k Ω 90.9   k Ω = 3.2   V