ZHCSJJ3E July   2009  – April 2019 TCA9555

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      简化原理图
  4. 4 修订历史记录
  5. 5 说明 （续）
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 I2C Interface Timing Requirements
    7. 7.7 Switching Characteristics
    8. 7.8 Typical Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 5-V Tolerant I/O Ports
      2. 9.3.2 Hardware Address Pins
      3. 9.3.3 Interrupt (INT) Output
    4. 9.4 Device Functional Modes
      1. 9.4.1 Power-On Reset (POR)
      2. 9.4.2 Powered-Up
    5. 9.5 Programming
      1. 9.5.1 I/O Port
      2. 9.5.2 I2C Interface
        1. 9.5.2.1 Bus Transactions
          1. 9.5.2.1.1 Writes
          2. 9.5.2.1.2 Reads
      3. 9.5.3 Device Address
      4. 9.5.4 Control Register and Command Byte
    6. 9.6 Register Maps
      1. 9.6.1 Register Descriptions
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Calculating Junction Temperature and Power Dissipation
        2. 10.2.2.2 Minimizing ICC When I/O Is Used to Control LED
        3. 10.2.2.3 Pull-Up Resistor Calculation
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13器件和文档支持
    1. 13.1 文档支持
      1. 13.1.1 相关文档
    2. 13.2 接收文档更新通知
    3. 13.3 社区资源
    4. 13.4 商标
    5. 13.5 静电放电警告
    6. 13.6 术语表
  14. 14机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

10.2.2.1 Calculating Junction Temperature and Power Dissipation

When designing with this device, it is important that the Recommended Operating Conditions not be violated. Many of the parameters of this device are rated based on junction temperature. So junction temperature must be calculated in order to verify that safe operation of the device is met. The basic equation for junction temperature is shown in Equation 1.

Equation 1. TCA9555 Equation_01_SCPS254.gif

θJA is the standard junction to ambient thermal resistance measurement of the package, as seen in the Thermal Information table. Pd is the total power dissipation of the device, and the approximation is shown in Equation 2.

Equation 2. TCA9555 Equation_02_SCPS254.gif

Equation 2 is the approximation of power dissipation in the device. The equation is the static power plus the summation of power dissipated by each port (with a different equation based on if the port is outputting high, or outputting low. If the port is set as an input, then power dissipation is the input leakage of the pin multiplied by the voltage on the pin). Note that this ignores power dissipation in the INT and SDA pins, assuming these transients to be small. They can easily be included in the power dissipation calculation by using Equation 3 to calculate the power dissipation in INT or SDA while they are pulling low, and this gives maximum power dissipation.

Equation 3. TCA9555 Equation_03_SCPS254.gif

Equation 3 shows the power dissipation for a single port which is set to output low. The power dissipated by the port is the VOL of the port multiplied by the current it is sinking.

Equation 4. TCA9555 Equation_04_SCPS254.gif

Equation 4 shows the power dissipation for a single port which is set to output high. The power dissipated by the port is the current sourced by the port multiplied by the voltage drop across the device (difference between VCC and the output voltage).
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