ZHCSBX0C december   2013  – may 2023 TPS65261 , TPS65261-1

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Revision History
  6. 5 Pin Configuration and Functions
  7. 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 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Adjusting the Output Voltage
      2. 7.3.2  Power Failure Detector
      3. 7.3.3  Enable and Adjusting Undervoltage Lockout
      4. 7.3.4  Soft-Start Time
      5. 7.3.5  Power Up Sequencing
        1. 7.3.5.1 External Power Sequencing
        2. 7.3.5.2 Automatic Power Sequencing
      6. 7.3.6  V7V Low Dropout Regulator and Bootstrap
      7. 7.3.7  Out-of-Phase Operation
      8. 7.3.8  Output Overvoltage Protection (OVP)
      9. 7.3.9  Slope Compensation
      10. 7.3.10 Overcurrent Protection
        1. 7.3.10.1 High-side MOSFET Overcurrent Protection
        2. 7.3.10.2 Low-side MOSFET Overcurrent Protection
      11. 7.3.11 Power Good
      12. 7.3.12 Adjustable Switching Frequency
      13. 7.3.13 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Pulse Skipping MODE (PSM)
  9. 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 Output Inductor Selection
        2. 8.2.2.2 Output Capacitor Selection
        3. 8.2.2.3 Input Capacitor Selection
        4. 8.2.2.4 Loop Compensation
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Parts
    2. 9.2 接收文档更新通知
    3. 9.3 支持资源
    4. 9.4 Trademarks
    5. 9.5 静电放电警告
    6. 9.6 术语表
  11. 10Mechanical, Packaging, and Orderable Information

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7.3.4 Soft-Start Time

The voltage on the respective SS pin controls the start-up of the buck output. When the voltage on the SS pin is less than the internal 0.6V reference, the TPS65261, TPS65261-1 regulates the internal feedback voltage to the voltage on the SS pin instead of 0.6V. The SS pin can be used to program an external soft-start function or to allow output of the buck to track another supply during start-up. The device has an internal pull-up current source of 5µA (typical) that charges an external soft-start capacitor to provide a linear ramping voltage at the SS pin. The TPS65261, TPS65261-1 regulates the internal feedback voltage to the voltage on the SS pin, allowing VOUT to rise smoothly from 0V to its regulated voltage without inrush current. The soft-start time can be calculated approximately by Equation 8.

Equation 8. GUID-34778329-F86A-40FB-860C-57EEF46E6640-low.gif

Many of the common power supply sequencing methods can be implemented using the SSx and ENx pins. Figure 7-6 shows the method implementing ratio-metric sequencing by connecting the SSx pins of three buck channels together. The regulator outputs ramp up and reach regulation at the same time. When calculating the soft-start time, the pull-up current source must be tripled in Equation 8.

GUID-7C20DA70-DB95-40A8-B6F4-C311808F8C96-low.gifFigure 7-6 Ratio Metric Power Up Using SSx Pins

Simultaneous power supply sequencing can be implemented by connecting capacitor to SSx pin, shown in Figure 7-7. The capacitors can be calculated using Equation 8 and Equation 9.

Equation 9. GUID-B29D53EB-0A73-4EEB-8A3A-4697EFFB69AB-low.gif
GUID-189EFDED-4FCD-42FE-8FE5-0E339F99C9A9-low.gifFigure 7-7 Simultaneous Startup Sequence Using SSx Pins