SLASE30 October   2020 DAC43401-Q1 , DAC53401-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  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  Timing Requirements: I2C Standard Mode
    7. 7.7  Timing Requirements: I2C Fast Mode
    8. 7.8  Timing Requirements: I2C Fast Mode Plus
    9. 7.9  Typical Characteristics: VDD = 1.8 V (Reference = VDD) or VDD = 2 V (Internal Reference)
    10. 7.10 Typical Characteristics: VDD = 5.5 V (Reference = VDD) or VDD = 5 V (Internal Reference)
    11. 7.11 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 Digital-to-Analog Converter (DAC) Architecture
        1. 8.3.1.1 Reference Selection and DAC Transfer Function
          1. 8.3.1.1.1 Power Supply as Reference
          2. 8.3.1.1.2 Internal Reference
      2. 8.3.2 DAC Update
        1. 8.3.2.1 DAC Update Busy
      3. 8.3.3 Nonvolatile Memory (EEPROM or NVM)
        1. 8.3.3.1 NVM Cyclic Redundancy Check
        2. 8.3.3.2 NVM_CRC_ALARM_USER Bit
        3. 8.3.3.3 NVM_CRC_ALARM_INTERNAL Bit
      4. 8.3.4 Programmable Slew Rate
      5. 8.3.5 Power-on-Reset (POR)
      6. 8.3.6 Software Reset
      7. 8.3.7 Device Lock Feature
      8. 8.3.8 PMBus Compatibility
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power Down Mode
      2. 8.4.2 Continuous Waveform Generation (CWG) Mode
      3. 8.4.3 PMBus Compatibility Mode
    5. 8.5 Programming
      1. 8.5.1 F/S Mode Protocol
      2. 8.5.2 I2C Update Sequence
        1. 8.5.2.1 Address Byte
        2. 8.5.2.2 Command Byte
      3. 8.5.3 I2C Read Sequence
    6. 8.6 Register Map
      1. 8.6.1 STATUS Register (address = D0h) [reset = 000Ch or 0014h]
      2. 8.6.2 GENERAL_CONFIG Register (address = D1h) [reset = 01F0h]
      3. 8.6.3 TRIGGER Register (address = D3h) [reset = 0008h]
      4. 8.6.4 DAC_DATA Register (address = 21h) [reset = 0000h]
      5. 8.6.5 DAC_MARGIN_HIGH Register (address = 25h) [reset = 0000h]
      6. 8.6.6 DAC_MARGIN_LOW Register (address = 26h) [reset = 0000h]
      7. 8.6.7 PMBUS_OPERATION Register (address = 01h) [reset = 0000h]
      8. 8.6.8 PMBUS_STATUS_BYTE Register (address = 78h) [reset = 0000h]
      9. 8.6.9 PMBUS_VERSION Register (address = 98h) [reset = 2200h]
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Programmable LED Biasing
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Power-Supply Margining
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    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 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9.2.1.2 Detailed Design Procedure

The DAC sets the source current of a MOSFET using the integrated buffer, as shown in Figure 9-1. Connect the LED between the power supply and the drain of the MOSFET. This configuration allows the DAC to control or set the amount of current through the LED. The integrated buffer controls the gate-source voltage of the MOSFET inside the feedback loop, thus compensating this drop and corresponding drift due to temperature, current, and ageing of the MOSFET. Calculate the value of the LED current set by the DAC using Equation 6. In order to generate 0 mA to 20 mA from a 0-V to 2.4-V DAC output range, the value of RSET resistor is 120-Ω. Select the internal reference with a span of 2x. Given a VGS of 1.2 V, the VDD of the DAC must be at least 3.6 V. Select a VDD of 5 V to allow variation of VGS across temperature. When the VDD headroom is a constraint, use a bipolar junction transistor (BJT) in place of the MOSFET. BJTs have much less VBE drop as compared to a VGS of a MOSFET. A MOSFET provides a much better match between the current through the set register and the LED current, as compared to a BJT.

Equation 6. GUID-20201022-CA0I-J03F-F3TV-CMNQ9C87PPSB-low.gif

The pseudocode for getting started with an LED biasing application is as follows:

//SYNTAX: WRITE <REGISTER NAME (Hex code)>, <MSB DATA>, <LSB DATA>
//Power-up the device, enable internal reference with 2x output span
WRITE GENERAL_CONFIG(0xD1), 0x11, 0xE5
//Write DAC code (12-bit aligned)
WRITE DAC_DATA(0x21), 0x07, 0xFC
//Write settings to the NVM
WRITE TRIGGER(0xD3), 0x00, 0x10