SLASEH2A November   2020  – May 2021 DAC61404 , DAC81404

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: Write, IOVDD: 1.7 V to 2.7 V
    7. 7.7  Timing Requirements: Write, IOVDD: 2.7 V to 5.5 V
    8. 7.8  Timing Requirements: Read and Daisy Chain, FSDO = 0, IOVDD: 1.7 V to 2.7 V
    9. 7.9  Timing Requirements: Read and Daisy Chain, FSDO = 1, IOVDD: 1.7 V to 2.7 V
    10. 7.10 Timing Requirements: Read and Daisy Chain, FSDO = 0, IOVDD: 2.7 V to 5.5 V
    11. 7.11 Timing Requirements: Read and Daisy Chain, FSDO = 1, IOVDD: 2.7 V to 5.5 V
    12. 7.12 Timing Diagrams
    13. 7.13 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 R-2R Ladder DAC
      2. 8.3.2 Programmable-Gain Output Buffer
        1. 8.3.2.1 Sense Pins
      3. 8.3.3 DAC Register Structure
        1. 8.3.3.1 DAC Output Update
          1. 8.3.3.1.1 Synchronous Update
          2. 8.3.3.1.2 Asynchronous Update
        2. 8.3.3.2 Broadcast DAC Register
        3. 8.3.3.3 Clear DAC Operation
      4. 8.3.4 Internal Reference
      5. 8.3.5 Power-On Reset (POR)
        1. 8.3.5.1 Hardware Reset
        2. 8.3.5.2 Software Reset
      6. 8.3.6 Thermal Alarm
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-Down Mode
    5. 8.5 Programming
      1. 8.5.1 Stand-Alone Operation
      2. 8.5.2 Daisy-Chain Operation
      3. 8.5.3 Frame Error Checking
    6. 8.6 Register Map
      1. 8.6.1  NOP Register (address = 00h) [reset = 0000h]
      2. 8.6.2  DEVICEID Register (address = 01h) [reset = 0A60h or 0920h]
      3. 8.6.3  STATUS Register (address = 02h) [reset = 0000h]
      4. 8.6.4  SPICONFIG Register (address = 03h) [reset = 0AA4h]
      5. 8.6.5  GENCONFIG Register (address = 04h) [reset = 4000h]
      6. 8.6.6  BRDCONFIG Register (address = 05h) [reset = 000Fh]
      7. 8.6.7  SYNCCONFIG Register (address = 06h) [reset = 0000h]
      8. 8.6.8  DACPWDWN Register (address = 09h) [reset = FFFFh]
      9. 8.6.9  DACRANGE Register (address = 0Ah) [reset = 0000h]
      10. 8.6.10 TRIGGER Register (address = 0Eh) [reset = 0000h]
      11. 8.6.11 BRDCAST Register (address = 0Fh) [reset = 0000h]
      12. 8.6.12 DACn Register (address = 10h to 13h) [reset = 0000h]
  9. 9 Application and Implementation
    1. 9.1 Application Information
    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
    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

9.2.2 Detailed Design Procedure

The DAC81404 is an excellent choice for this application because of the device exceptional linearity and noise performance. The maximum bipolar output voltage requirement is ±20 V; therefore, set the AVDD and AVSS supplies to 21 V and −21 V, respectively. For a unipolar output range, set the AVDD supply to 41 V for a full-scale output voltage of 40 V. In unipolar designs, the AVSS supply can be tied to ground. In all cases, the supply voltages must be selected so that the AVDD − AVSS voltage does not exceed 41.5 V.

The output stage is designed as a standard class AB output because of the design simplicity. A current limit stage can be designed to limit the current in the output stage during a short-circuit event.

A simple diode-and-resistor-based biasing is chosen for the class AB output stage. A small constant current flows through the series circuit of R1, D1, D2 and R2, producing symmetrical voltage drops on either side of the input. With no input voltage applied, the point between the two diodes is 0 V. As current flows through the chain, there is a forward-bias voltage drop of approximately 0.7 V across the diodes that are applied to the base-emitter junctions of the switching transistors. Therefore, the voltage drop across the diodes biases the base of transistor T1 to approximately 0.7 V, and the base of transistor T2 to approximately −0.7 V. Therefore, the two silicon diodes provide a constant voltage drop of approximately 1.4 V between the two bases biasing them above cutoff.

Current and voltage is sensed and fed to an ADC to close the loop for the completion of the circuit. The device has sense connections for sensing the output and load ground voltages. One of the key features of this device is load-ground voltage compensation, which can be used in this design. The load ground and device ground difference must be within ±12 V.

The R1 and R2 values are decided by how much quiescent current is required by the design biasing scheme. Figure 9-2 and Figure 9-3 show simulation results of the output voltage programmed from −10 V to +10 V, while providing a constant 100 mA current to the load.