SLVSEW2A September   2020  – August 2021 TPS54618C-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  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 and Output Current
      3. 7.3.3  Bootstrap Voltage (Boot) and Low Dropout Operation
      4. 7.3.4  Error Amplifier
      5. 7.3.5  Voltage Reference
      6. 7.3.6  Adjusting the Output Voltage
      7. 7.3.7  Enable and Adjusting Undervoltage Lockout
      8. 7.3.8  Soft-Start Pin
      9. 7.3.9  Sequencing
      10. 7.3.10 Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
      11. 7.3.11 Overcurrent Protection
      12. 7.3.12 Frequency Shift
      13. 7.3.13 Reverse Overcurrent Protection
      14. 7.3.14 Synchronize Using the RT/CLK Pin
      15. 7.3.15 Power Good (PWRGD Pin)
      16. 7.3.16 Overvoltage Transient Protection
      17. 7.3.17 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Simple Small Signal Model for Peak Current Mode Control
      2. 7.4.2 Small Signal Model for Frequency Compensation
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Step One: Select the Switching Frequency
        2. 8.2.2.2 Step Two: Select the Output Inductor
        3. 8.2.2.3 Step Three: Choose the Output Capacitor
        4. 8.2.2.4 Step Four: Select the Input Capacitor
        5. 8.2.2.5 Step Five: Choose the Soft-Start Capacitor
        6. 8.2.2.6 Step Six: Select the Bootstrap Capacitor
        7. 8.2.2.7 Step Eight: Select Output Voltage and Feedback Resistors
          1. 8.2.2.7.1 Output Voltage Limitations
        8. 8.2.2.8 Step Nine: Select Loop Compensation Components
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Power Dissipation Estimate
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Developmental Support
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    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

7.3.7 Enable and Adjusting Undervoltage Lockout

The TPS54618C-Q1 is disabled when the VIN pin voltage falls below 2.28 V. If an application requires a higher undervoltage lockout (UVLO), use the EN pin as shown in Figure 7-2 to adjust the input voltage UVLO by using two external resistors. TI recommends using the EN resistors to set the UVLO falling threshold (VSTOP) above 2.6 V. The rising threshold (VSTART) must be set to provide enough hysteresis to allow for any input supply variations. The EN pin has an internal pullup current source that provides the default condition of the TPS54618C-Q1 operating when the EN pin floats. Once the EN pin voltage exceeds 1.25 V, an additional 1.6 μA of hysteresis is added. When the EN pin is pulled below 1.18 V, the 1.6 μA is removed. This additional current facilitates input voltage hysteresis.

GUID-A490056E-B136-43E2-BAF6-5945D2055973-low.gifFigure 7-2 Adjustable Undervoltage Lockout
Equation 2. GUID-A59656CB-9DE7-48D0-BD44-F4E6227E9C6F-low.gif

Equation 3. GUID-19E710B2-49FB-41FF-B9D7-984594F8FEBA-low.gif

where

  • R1 and R2 are in Ω
  • Ih = 1.6 µA
  • Ip = 1.9 µA
  • VENRISING = 1.25 V
  • VENFALLING = 1.18 V