ZHCSKY4B November   2018  – December 2020 TPS55288

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 Pin Configuration and 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 I2C Timing Characteristics
    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  VCC Power Supply
      2. 7.3.2  Operation Mode Setting
      3. 7.3.3  Input Undervoltage Lockout
      4. 7.3.4  Enable and Programmable UVLO
      5. 7.3.5  Soft Start
      6. 7.3.6  Shutdown and Load Discharge
      7. 7.3.7  Switching Frequency
      8. 7.3.8  Switching Frequency Dithering
      9. 7.3.9  Inductor Current Limit
      10. 7.3.10 Internal Charge Path
      11. 7.3.11 Output Voltage Setting
      12. 7.3.12 Output Current Monitoring and Cable Voltage Droop Compensation
      13. 7.3.13 Integrated Gate Drivers
      14. 7.3.14 Output Current Limit
      15. 7.3.15 Overvoltage Protection
      16. 7.3.16 Output Short Circuit Protection
      17. 7.3.17 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 PWM Mode
      2. 7.4.2 Power Save Mode
    5. 7.5 I2C Serial Interface
      1. 7.5.1 Data Validity
      2. 7.5.2 START and STOP Conditions
      3. 7.5.3 Byte Format
      4. 7.5.4 Acknowledge (ACK) and Not Acknowledge (NACK)
      5. 7.5.5 Slave Address and Data Direction Bit
      6. 7.5.6 Single Read and Write
      7. 7.5.7 Multi-Read and Multi-Write
    6. 7.6 Register Maps
      1. 7.6.1 REF Register (Address = 0h, 1h) [reset = 11010010h, 00000000h]
      2. 7.6.2 IOUT_LIMIT Register (Address = 2h) [reset = 11100100h]
      3. 7.6.3 VOUT_SR Register (Address = 3h) [reset = 00000001h]
      4. 7.6.4 VOUT_FS Register (Address = 4h) [reset = 00000011h]
      5. 7.6.5 CDC Register (Address = 5h) [reset = 11100000h]
      6. 7.6.6 MODE Register (Address = 6h) [reset = 00100000h]
      7. 7.6.7 STATUS Register (Address = 7h) [reset = 00000011h]
      8. 7.6.8 Register Summary
  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 USB PD Power Supply Detailed Design Procedure
        1. 8.2.2.1 Switching Frequency
        2. 8.2.2.2 Output Voltage Setting
        3. 8.2.2.3 Inductor Selection
        4. 8.2.2.4 Input Capacitor
        5. 8.2.2.5 Output Capacitor
        6. 8.2.2.6 Output Current Limit
        7. 8.2.2.7 Loop Stability
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 第三方产品免责声明
    2. 11.2 接收文档更新通知
    3. 11.3 支持资源
    4. 11.4 Trademarks
    5. 11.5 静电放电警告
    6. 11.6 术语表
  12. 12Mechanical, Packaging, and Orderable Information

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7.3.4 Enable and Programmable UVLO

The TPS55288 has a dual function enable and undervoltage lockout (UVLO) circuit. When the input voltage at the VIN pin is above the input UVLO rising threshold of 3 V and the EN/UVLO pin is pulled above 1.15 V but less than the enable UVLO threshold of 1.23 V, the TPS55288 is enabled but still in standby mode. The TPS55288 starts to detect the resistance between the MODE pin and ground. After that, the TPS55288 selects the power supply for VCC, the I2C slave address, and the PFM or FPWM mode for light load condition accordingly.

The EN/UVLO pin has an accurate UVLO voltage threshold to support programmable input undervoltage lockout with hysteresis. When the EN/UVLO pin voltage is greater than the UVLO threshold of 1.23 V, the TPS55288 is enabled for I2C communication and switching operation. A hysteresis current IUVLO_HYS is sourced out of the EN/UVLO pin to provide hysteresis that prevents on/off chattering in the presence of noise with a slowly changing input voltage.

By using resistor divider as shown in Figure 7-1, the turnon threshold is calculated using Equation 1.

Equation 1. GUID-BF07E82C-1278-47FB-A41F-055D6ACF116C-low.gif

where

  • VUVLO is the UVLO threshold of 1.23 V at the EN/UVLO pin

The hysteresis between the UVLO turnon threshold and turnoff threshold is set by the upper resistor in the EN/UVLO resistor divider and is given by the Equation 2.

Equation 2. GUID-12A088C2-9430-48BA-BCDE-8B1E6882A9C5-low.gif

where

  • IUVLO_HYS is the sourcing current from the EN/UVLO pin when the voltage at the EN/UVLO pin is above VUVLO
GUID-20200817-CA0I-DGNZ-G7DK-KTB4WDSHJVWX-low.gif Figure 7-1 Programmable UVLO With Resistor Divider at the EN/UVLO pin

Using an NMOSFET together with a resistor divider can implement both logic enable and programmable UVLO as shown in Figure 7-2. The EN logic high level must be greater than enable threshold plus the Vth of the NMOSFET Q1. The Q1 also eliminates the leakage current from VIN to ground through the UVLO resistor divider during shutdown mode.

GUID-20200817-CA0I-F13J-Q1WP-88DKKWDPQSKH-low.gif Figure 7-2 Logic Enable and Programmable UVLO