SLVSFJ9 September   2021 TPS25854-Q1 , TPS25855-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (Continued)
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Timing Requirements
    7. 8.7 Switching Characteristics
    8. 8.8 Typical Characteristics
  9. 9 Parameter Measurement Information
  10. 10Detailed Description
    1. 10.1 Overview
    2. 10.2 Functional Block Diagram
    3. 10.3 Feature Description
      1. 10.3.1  Power Down or Undervoltage Lockout
      2. 10.3.2  Input Overvoltage Protection (OVP) - Continuously Monitored
      3. 10.3.3  Buck Converter
      4. 10.3.4  FREQ/SYNC
      5. 10.3.5  Bootstrap Voltage (BOOT)
      6. 10.3.6  Minimum ON-time, Minimum OFF-time
      7. 10.3.7  Internal Compensation
      8. 10.3.8  Current Limit and Short Circuit Protection
        1. 10.3.8.1 USB Switch Programmable Current Limit (ILIM)
        2. 10.3.8.2 Cycle-by-Cycle Buck Current Limit
        3. 10.3.8.3 OUT Current Limit
      9. 10.3.9  Cable Compensation
      10. 10.3.10 Thermal Management With Temperature Sensing (TS) and OTSD
      11. 10.3.11 Thermal Shutdown
      12. 10.3.12 FAULT Indication
      13. 10.3.13 USB Specification Overview
      14. 10.3.14 USB Type-C® Basics
        1. 10.3.14.1 Configuration Channel
        2. 10.3.14.2 Detecting a Connection
        3. 10.3.14.3 Plug Polarity Detection
      15. 10.3.15 USB Port Operating Modes
        1. 10.3.15.1 USB Type-C® Mode
        2. 10.3.15.2 Dedicated Charging Port (DCP) Mode
          1. 10.3.15.2.1 DCP BC1.2 and YD/T 1591-2009
          2. 10.3.15.2.2 DCP Divider-Charging Scheme
          3. 10.3.15.2.3 DCP 1.2-V Charging Scheme
        3. 10.3.15.3 DCP Auto Mode
    4. 10.4 Device Functional Modes
      1. 10.4.1 Shutdown Mode
      2. 10.4.2 Active Mode
  11. 11Application and Implementation
    1. 11.1 Application Information
    2. 11.2 Typical Applications
      1. 11.2.1 Design Requirements
      2. 11.2.2 Detailed Design Procedure
        1. 11.2.2.1 Output Voltage Setting
        2. 11.2.2.2 Switching Frequency
        3. 11.2.2.3 Inductor Selection
        4. 11.2.2.4 Output Capacitor Selection
        5. 11.2.2.5 Input Capacitor Selection
        6. 11.2.2.6 Bootstrap Capacitor Selection
        7. 11.2.2.7 Undervoltage Lockout Set-Point
        8. 11.2.2.8 Cable Compensation Set-Point
        9. 11.2.2.9 FAULT, POL, and THERM_WARN Resistor Selection
      3. 11.2.3 Application Curves
  12. 12Power Supply Recommendations
  13. 13Layout
    1. 13.1 Layout Guidelines
    2. 13.2 Layout Example
    3. 13.3 Ground Plane and Thermal Considerations
  14. 14Device and Documentation Support
    1. 14.1 Receiving Notification of Documentation Updates
    2. 14.2 Support Resources
    3. 14.3 Trademarks
    4. 14.4 Electrostatic Discharge Caution
    5. 14.5 Glossary
  15. 15Mechanical, Packaging, and Orderable Information

Package Options

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

10.3.6 Minimum ON-time, Minimum OFF-time

Minimum ON-time, TON_MIN, is the smallest duration of time that the HS switch can be on. TON_MIN is typically 84 ns in the TPS2585x-Q1. Minimum OFF-time, TOFF_MIN, is the smallest duration that the HS switch can be off. TOFF_MIN is typically 81 ns in the TPS2585x-Q1. In CCM (FPWM) operation, TON_MIN and TOFF_MIN  limit the voltage conversion range given a selected switching frequency.

The minimum duty cycle allowed is:

Equation 5. DMIN = TON_MIN × fSW

And the maximum duty cycle allowed is:

Equation 6. DMAX = 1 – TOFF_MIN × fSW

Given fixed TON_MIN and TOFF_MIN, the higher the switching frequency the narrower the range of the allowed duty cycle.

Given an output voltage, the choice of the switching frequency affects the allowed input voltage range, solution size and efficiency. The maximum operation supply voltage can be found by:

Equation 7. GUID-3922E2DB-A0A2-46C1-85E4-348841D22BB8-low.gif

At lower supply voltage, the switching frequency is limited by TOFF_MIN. The minimum VIN can be approximated by:

Equation 8. GUID-54852D19-1A6B-4D15-BBA9-BA919C4A0DF4-low.gif

Taking considerations of power losses in the system with heavy load operation, VIN_MAX is higher than the result calculated in Equation 7.

If minimum ON-time or minimum OFF-time do not support the desired conversion ratio, frequency is reduced automatically allowing regulation to maintain during load dump and with very low dropout during cold crank even with high operating-frequency setting.