JAJSES9 February   2018 DAC8771

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      DAC8771のブロック図
  4. 4 改訂履歴
  5. 5 Device Comparison Table
  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 Timing Requirements: Write and Readback Mode
    7. 7.7 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  Current Output Stage
      2. 8.3.2  Voltage Output Stage
      3. 8.3.3  Buck-Boost Converter
        1. 8.3.3.1 Buck-Boost Converter Outputs
        2. 8.3.3.2 Selecting and Enabling Buck-Boost Converter
        3. 8.3.3.3 Configurable Clamp Feature and Current Output Settling Time
          1. 8.3.3.3.1 Default Mode - CCLP[1:0] = "00"
          2. 8.3.3.3.2 Fixed Clamp Mode - CCLP[1:0] = "01"
          3. 8.3.3.3.3 Auto Learn Mode - CCLP[1:0] = "10"
          4. 8.3.3.3.4 High Side Clamp (HSCLMP)
      4. 8.3.4  Analog Power Supply
      5. 8.3.5  Digital Power Supply
      6. 8.3.6  Internal Reference
      7. 8.3.7  Power-On-Reset
      8. 8.3.8  ALARM Pin
      9. 8.3.9  Power GOOD bit
      10. 8.3.10 Status Register
      11. 8.3.11 Status Mask
      12. 8.3.12 Alarm Action
      13. 8.3.13 Watchdog Timer
      14. 8.3.14 Programmable Slew Rate
      15. 8.3.15 HART Interface
    4. 8.4 Device Functional Modes
      1. 8.4.1 Serial Peripheral Interface (SPI)
        1. 8.4.1.1 Stand-Alone Operation
        2. 8.4.1.2 Daisy-Chain Operation
      2. 8.4.2 SPI Shift Register
      3. 8.4.3 Write Operation
      4. 8.4.4 Read Operation
      5. 8.4.5 Updating the DAC Outputs and LDAC Pin
        1. 8.4.5.1 Asynchronous Mode
        2. 8.4.5.2 Synchronous Mode
      6. 8.4.6 Hardware RESET Pin
      7. 8.4.7 Hardware CLR Pin
      8. 8.4.8 Frame Error Checking
      9. 8.4.9 DAC Data Calibration
        1. 8.4.9.1 DAC Data Gain and Offset Calibration Registers
    5. 8.5 Register Maps
      1. 8.5.1 Register Maps
        1. 8.5.1.1 DAC8771 Commands
        2. 8.5.1.2 Register Maps and Bit Functions
          1. 8.5.1.2.1  No Operation Register (address = 0x00) [reset = 0x0000]
            1. Table 6. No Operation Field Descriptions
          2. 8.5.1.2.2  Reset Register (address = 0x01) [reset = 0x0000]
            1. Table 7. Reset Register Field Descriptions
          3. 8.5.1.2.3  Reset Config Register (address = 0x02) [reset = 0x0000]
            1. Table 8. Reset Config Register Field Descriptions
          4. 8.5.1.2.4  Select DAC Register (address = 0x03) [reset = 0x0000]
            1. Table 9. Select DAC Register Field Descriptions
          5. 8.5.1.2.5  Configuration DAC Register (address = 0x04) [reset = 0x0000]
            1. Table 10. Configuration DAC Register Field Descriptions
          6. 8.5.1.2.6  DAC Data Register (address = 0x05) [reset = 0x0000]
            1. Table 11. DAC Data Register Field Descriptions
          7. 8.5.1.2.7  Select Buck-Boost Converter Register (address = 0x06) [reset = 0x0000]
            1. Table 12. Select Buck-Boost Converter Register Field Descriptions
          8. 8.5.1.2.8  Configuration Buck-Boost Register (address = 0x07) [reset = 0x0000]
            1. Table 13. Configuration Buck-Boost Register Field Descriptions
          9. 8.5.1.2.9  DAC Channel Calibration Enable Register (address = 0x08) [reset = 0x0000]
            1. Table 14. DAC Channel Calibration Enable Register Field Descriptions
          10. 8.5.1.2.10 DAC Channel Gain Calibration Register (address = 0x09) [reset = 0x0000]
            1. Table 15. DAC Channel Gain Calibration Register Field Descriptions
          11. 8.5.1.2.11 DAC Channel Offset Calibration Register (address = 0x0A) [reset = 0x0000]
            1. Table 16. DAC Channel Offset Calibration Register Field Descriptions
          12. 8.5.1.2.12 Status Register (address = 0x0B) [reset = 0x1000]
            1. Table 17. Status Register Field Descriptions
          13. 8.5.1.2.13 Status Mask Register (address = 0x0C) [reset = 0x0000]
            1. Table 18. Status Mask Register Field Descriptions
          14. 8.5.1.2.14 Alarm Action Register (address = 0x0D) [reset = 0x0000]
            1. Table 19. Alarm Action Register Field Descriptions
          15. 8.5.1.2.15 User Alarm Code Register (address = 0x0E) [reset = 0x0000]
            1. Table 20. User Alarm Code Register Field Descriptions
          16. 8.5.1.2.16 Reserved Register (address = 0x0F) [reset = N/A]
            1. Table 21. Reserved Register Field Descriptions
          17. 8.5.1.2.17 Write Watchdog Timer Register (address = 0x10) [reset = 0x0000]
            1. Table 22. Write Watchdog Timer Register Field Descriptions
          18. 8.5.1.2.18 Reserved Register (address 0x12 - 0xFF) [reset = N/A]
            1. Table 23. Reserved Register Field Descriptions
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Buck-Boost Converter External Component Selection
      2. 9.1.2 Voltage and Current Outputs on a Shared Terminal
      3. 9.1.3 Optimizing Current Output Settling Time with Auto-Learn Mode
      4. 9.1.4 Protection for Industrial Transients
      5. 9.1.5 Implementing HART with DAC8771
    2. 9.2 Typical Application
      1. 9.2.1 Single-Channel, Isolated, EMC and EMI Protected Analog Output Module with Adaptive Power Management
      2. 9.2.2 Design Requirements
      3. 9.2.3 Detailed Design Procedure
      4. 9.2.4 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12デバイスおよびドキュメントのサポート
    1. 12.1 デバイス・サポート
      1. 12.1.1 デベロッパー・ネットワークの製品に関する免責事項
    2. 12.2 ドキュメントのサポート
      1. 12.2.1 関連資料
    3. 12.3 ドキュメントの更新通知を受け取る方法
    4. 12.4 コミュニティ・リソース
    5. 12.5 商標
    6. 12.6 静電気放電に関する注意事項
    7. 12.7 Glossary
  13. 13メカニカル、パッケージ、および注文情報

8.3.3 Buck-Boost Converter

The DAC8771 includes a Buck-Boost Converter to minimize the power dissipation of the chip and provides significant system integration. This Buck-Boost converter is based on a Single Inductor Multiple Output (SIMO) architecture and requires a single inductor to simultaneously generate all the analog power supplies required by the chip. The Buck-Boost converter uses three on-chip switches (shown in Figure 99) which are synchronously controlled via current mode control logic. The DC/DC converter is designed to work in discontinuous conduction mode (DCM) with an external inductor of value 100 µH connected between LN and LP pins (see Buck-Boost Converter External Component Selection section). The peak inductor current inductor is limited to a value of 0.5 A internally.

DAC8771 BuckBoostConv_SLASEE2_DAC8771.gifFigure 99. Buck-Boost Converter

The Buck-Boost converter employs a variable switching frequency technique. This technique increases the converter efficiency at all loads by automatically reducing the switching frequency at light loads and increasing it at heavy loads. At no load condition, the converter stops switching completely until the load capacitor discharges by a preset voltage. At this point, the converter automatically starts switching and recharges the load capacitor(s). In addition to saving power at all loads, this technique ensures low switching noise on the converter outputs at light loads. The minimum load capacitor for the Buck-Boost converter is 10 µF. This capacitor must be connected between the Schottky diode(s) and ground (0 V) for each arm of the Buck-Boost converter. The Buck-Boost converter, when enabled, generates ripples on the supply pins (VPOS_IN and VNEG_IN). This ripple is typically attenuated by the power supply rejection ratio of the output amplifiers (IOUT or VOUT) and appears as noise on the output pin of the amplifiers (IOUT and VOUT). A larger load capacitor in combination with additional filter (see application section) reduces the output ripple at the expense of increasing settling time of the converter output.

The input voltage to the Buck-Boost converter (pin PVDD) can vary from +12 V to +36 V. These outputs can be individually enabled or disabled via the user SPI interface (See Commands in Table 4 and Table 5).