ZHCSM85A October   2020  – September 2023 DAC43701-Q1 , DAC53701-Q1

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: I2C Standard Mode
    7. 6.7  Timing Requirements: I2C Fast Mode
    8. 6.8  Timing Requirements: I2C Fast-Mode Plus
    9. 6.9  Timing Requirements: GPI
    10. 6.10 Timing Diagram
    11. 6.11 Typical Characteristics: VDD = 5.5 V (Reference = VDD) or VDD = 5 V (Internal Reference)
    12. 6.12 Typical Characteristics: VDD = 1.8 V (Reference = VDD) or VDD = 2 V (Internal Reference)
    13. 6.13 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 Digital-to-Analog Converter (DAC) Architecture
        1. 7.3.1.1 Reference Selection and DAC Transfer Function
          1. 7.3.1.1.1 Power Supply as Reference
          2. 7.3.1.1.2 Internal Reference
      2. 7.3.2 General-Purpose Input (GPI)
      3. 7.3.3 DAC Update
        1. 7.3.3.1 DAC Update Busy
      4. 7.3.4 Nonvolatile Memory (EEPROM or NVM)
        1. 7.3.4.1 NVM Cyclic Redundancy Check
        2. 7.3.4.2 NVM_CRC_ALARM_USER Bit
        3. 7.3.4.3 NVM_CRC_ALARM_INTERNAL Bit
      5. 7.3.5 Programmable Slew Rate
      6. 7.3.6 Power-On Reset (POR)
      7. 7.3.7 Software Reset
      8. 7.3.8 Device Lock Feature
      9. 7.3.9 PMBus Compatibility
    4. 7.4 Device Functional Modes
      1. 7.4.1 Power Down Mode
      2. 7.4.2 Continuous Waveform Generation (CWG) Mode
      3. 7.4.3 PMBus Compatibility Mode
    5. 7.5 Programming
      1. 7.5.1 F/S Mode Protocol
      2. 7.5.2 I2C Update Sequence
        1. 7.5.2.1 Address Byte
          1. 7.5.2.1.1 Target Address Configuration
        2. 7.5.2.2 Command Byte
      3. 7.5.3 I2C Read Sequence
    6. 7.6 Register Map
      1. 7.6.1  STATUS Register (address = D0h) [reset = 000Ch or 0014h]
      2. 7.6.2  GENERAL_CONFIG Register (address = D1h) [reset = 01F0h]
      3. 7.6.3  CONFIG2 Register (address = D2h) [reset = device-specific]
      4. 7.6.4  TRIGGER Register (address = D3h) [reset = 0008h]
      5. 7.6.5  DAC_DATA Register (address = 21h) [reset = 0000h]
      6. 7.6.6  DAC_MARGIN_HIGH Register (address = 25h) [reset = device-specific]
      7. 7.6.7  DAC_MARGIN_LOW Register (address = 26h) [reset =device-specific]
      8. 7.6.8  PMBUS_OPERATION Register (address = 01h) [reset = 0000h]
      9. 7.6.9  PMBUS_STATUS_BYTE Register (address = 78h) [reset = 0000h]
      10. 7.6.10 PMBUS_VERSION Register (address = 98h) [reset = 2200h]
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Power-Supply Margining
        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 LED Thermal Foldback
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
    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 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 接收文档更新通知
    3. 9.3 支持资源
    4. 9.4 Trademarks
    5. 9.5 静电放电警告
    6. 9.6 术语表
  11. 10Mechanical, Packaging, and Orderable Information

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8.2.2.2 Detailed Design Procedure

Choose a 5-V Zener diode of less than 50 μA of reverse current. The DACx3701-Q1consumes a quiescent current of around 200 μA. Assume the load current of the DAC to be maximum 500 μA. Thus, the total current needed for the DAC and the Zener diode is 750 μA. Considering a 2 × derating factor, design the circuit for 1.5 mA. Hence, the value of the current limiting resistor RZ is (12 V – 5 V) / 1.5 mA = 4.7 kΩ. The worst-case power dissipation across the Zener diode is (5 V × 1.5 mA) = 7.5 mW. Any standard Zener diode can be used with this power rating.

Choose a negative temperature coefficient (NTC) thermistor with nominal resistance of 10 kΩ at 25°C. At the foldback point of 30°C, the resistance of the NTC, RNTC is approximately 7 kΩ. At 105°C, the resistance of the NTC is approximately 800 Ω. Choose the value of R after simulating the linearity plot along with the correct NTC part number. For the sake of calculation, take R as 5 kΩ. In this case, VFB is 2.08 V at 25°C (RNTC = 7 kΩ). For 10‑bit resolution and a full-scale output of 5 V, 2.08 V corresponds to the DAC code (2.08 × 1024 / 5) = 426. Similarly, the LED must be cut off at 105°C, which refers to an RNTC of 800 Ω and a corresponding VFB of 4.31 V, or the DAC code 883. Thus, the margin-high value is 883, or 0x373, and the margin-low value is 426, or 0x1AA.

Configure the FUNC_CONFIG bits to 00b in the GENERAL_CONFIG register to select triangular waveform. Use Equation 5 for calculating the frequency of the triangular waveform. By choosing a CODE_STEP of 6 LSB and SLEW_RATE of (25.6 μs × 1.25), the frequency of the triangular waveform is 205 Hz.

For voltage output, use an RC filter as shown in Figure 8-4. The resistor divider comprised of R1, R2, and R3 define the voltage below the foldback temperature. This voltage divider is useful in case the maximum LED current is set below the 100% value.