ZHCSG04F january   2017  – may 2023 TPS65235-1

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 Timing Requirements
    7. 6.7 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  Boost Converter
      2. 7.3.2  Linear Regulator and Current Limit
      3. 7.3.3  Boost Converter Current Limit
      4. 7.3.4  Charge Pump
      5. 7.3.5  Slew Rate Control
      6. 7.3.6  Short-Circuit Protection, Hiccup, and Overtemperature Protection
      7. 7.3.7  Tone Generation
      8. 7.3.8  Tone Detection
      9. 7.3.9  Audio Noise Rejection
      10. 7.3.10 Disable and Enable
      11. 7.3.11 Component Selection
        1. 7.3.11.1 Boost Inductor
        2. 7.3.11.2 Capacitor Selection
        3. 7.3.11.3 Surge Components
        4. 7.3.11.4 Consideration for Boost Filtering and LNB Noise
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1 Serial Interface Description
      2. 7.5.2 TPS65235-1 I2C Update Sequence
    6. 7.6 Register Maps
      1. 7.6.1 Control Register 1 (address = 0x00) [reset = 0x08]
      2. 7.6.2 Control Register 2 (address = 0x01) [reset = 0x09]
      3. 7.6.3 Status Register (address = 0x02) [reset = 0x29]
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 DiSEqc1.x Support
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
      2. 8.2.2 DiSEqc2.x Support
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curve
    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 Device Support
      1. 9.1.1 第三方产品免责声明
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 接收文档更新通知
    4. 9.4 支持资源
    5. 9.5 Trademarks
    6. 9.6 静电放电警告
    7. 9.7 术语表
  11. 10Mechanical, Packaging, and Orderable Information

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7.3.5 Slew Rate Control

When LNB output voltage transits from 13.4 V to 18.2 V or 18.2 V to 13.4 V , the cap at pin TCAP controls the transition time. This transition time makes sure the boost converter output to follow LNB output change. Usually boost converter has low bandwidth and can’t response fast. The voltage at TCAP acts as the reference voltage of the linear regulator. The boost converter’s reference is also based on TCAP with additional fixed voltage to generate a 0.8 V above the LNB output.

The charging and discharging current is 10 µA, thus the transition time can be estimated as:

Equation 4. t T C A P   m s   =   0.8   ×   C S S   n F I S S   μ A

A 22-nF capacitor generates about 2 ms transition time.

In light load conditions, when LNB output voltage is set from 18.2 V to 13.4 V, the voltage drops very slow, which causes wrong VOUT_GOOD (Bit 0 at status register 0x02) logic for LNB output voltage detection. TPS65235-1 has integrated a pull down circuit to pull down the output during the transition. This ensures the voltage change can follow the voltage at TCAP. When the 22-kHz tone signal is superimposing on the LNB output voltage, the pull down current can also provide square wave instead of a distorted waveforms.