JAJSEF2D June   2013  – December 2021 DAC7760 , DAC8760

PRODUCTION DATA  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and 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  Electrical Characteristics: AC
    7. 7.7  Timing Requirements: Write Mode
    8. 7.8  Timing Requirements: Readback Mode
    9. 7.9  Timing Diagrams
    10. 7.10 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  DAC Architecture
      2. 8.3.2  Voltage Output Stage
      3. 8.3.3  Current Output Stage
      4. 8.3.4  Internal Reference
      5. 8.3.5  Digital Power Supply
      6. 8.3.6  DAC Clear
      7. 8.3.7  Power-On Reset
      8. 8.3.8  Alarm Detection
      9. 8.3.9  Watchdog Timer
      10. 8.3.10 Frame Error Checking
      11. 8.3.11 User Calibration
      12. 8.3.12 Programmable Slew Rate
    4. 8.4 Device Functional Modes
      1. 8.4.1 Setting Voltage and Current Output Ranges
      2. 8.4.2 Boost Configuration for IOUT
      3. 8.4.3 Filtering the Current Output (only on the VQFN package)
      4. 8.4.4 HART Interface
        1. 8.4.4.1 For 4-mA to 20-mA Mode
        2. 8.4.4.2 For All Current Output Modes
    5. 8.5 Programming
      1. 8.5.1 Serial Peripheral Interface (SPI)
        1. 8.5.1.1 SPI Shift Register
        2. 8.5.1.2 Write Operation
        3. 8.5.1.3 Read Operation
        4. 8.5.1.4 Stand-Alone Operation
        5. 8.5.1.5 Multiple Devices on the Bus
    6. 8.6 Register Maps
      1. 8.6.1 DACx760 Command and Register Map
        1. 8.6.1.1 DACx760 Register Descriptions
          1. 8.6.1.1.1 Control Register
          2. 8.6.1.1.2 Configuration Register
          3. 8.6.1.1.3 DAC Registers
          4. 8.6.1.1.4 Reset Register
          5. 8.6.1.1.5 Status Register
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Controlling the VOUT and IOUT Pins
        1. 9.1.1.1 VOUT and IOUT Pins are Independent Outputs, Never Simultaneously Enabled
        2. 9.1.1.2 VOUT and IOUT Pins are Independent Outputs, Simultaneously Enabled
        3. 9.1.1.3 VOUT and IOUT Pins are Tied Together, Never Simultaneously Enabled
      2. 9.1.2 Implementing HART in All Current Output Modes
        1. 9.1.2.1 Using CAP2 Pin on VQFN Package
        2. 9.1.2.2 Using the ISET-R Pin
      3. 9.1.3 Short-Circuit Current Limiting
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Thermal Considerations
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 サポート・リソース
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

11.1.1 Thermal Considerations

The DACx760 is designed for a maximum junction temperature of +150°C. In cases where the maximum AVDD is driving maximum current into ground, this could be exceeded. Use the following equation, from Section 7.1, to determine the maximum junction temperature that can be reached:

Equation 8. Power Dissipation = (TJmax – TA)/θJA

where

  • TJmax = 150°C
  • TA is the ambient temperature
  • θJA is the package dependent junction-to-ambient thermal resistance, which is found in Section 7.4

The power dissipation can be calculated by multiplying all the supply voltages with the currents supplied, which is found in the Power Requirements subsection of Section 7.5.

Consider an example: IOUT is enabled, supplying 24 mA into GND with a 25°C ambient temperature, AVDD of 24 V, AVSS is tied to GND and DVDD is generated internally. From the specifications table, the maximum value of AIDD = 3 mA when IOUT is enabled and DAC code = 0x0000. Also, the maximum value of DIDD = 1 mA. Accordingly, the worst case power dissipation is 24 V × (24 mA + 3 mA + 1 mA) = 672 mW. Using the RθJA value for the TSSOP package, we get TJmax = 25°C + (32.3 × 0.672)°C = 46.7°C. At 85°C ambient temperature, the corresponding value of TJmax is 106.7°C. Using this type of analysis, the system designer can both specify and design for the equipment operating conditions. Note that the thermal pad in both packages is recommended to be connected to a copper plane for enhanced thermal performance.