SBAS337E April   2005  – March 2018 DAC7811

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Block Diagram
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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 Typical Characteristics: VDD = 5 V
    7. 6.7 Typical Characteristics: VDD = 2.7 V
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
    4. 7.4 Device Functional Modes
      1. 7.4.1 Serial Interface
      2. 7.4.2 Input Shift Register
      3. 7.4.3 SYNC Interrupt (Stand-Alone Mode)
      4. 7.4.4 Daisy-Chain
      5. 7.4.5 Control Bits C3 to C0
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Unipolar Operation Using DAC7811
      2. 8.1.2 Bipolar Operation Using the DAC7811
      3. 8.1.3 Stability Circuit
      4. 8.1.4 Amplifier Selection
      5. 8.1.5 Programmable Current Source Circuit
    2. 8.2 Typical Application
      1. 8.2.1 Single Supply Unipolar Multiplying DAC
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resource
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3 Feature Description

The DAC7811 is a single channel, current output, 12-bit digital-to-analog converter (DAC). The architecture, illustrated in Figure 25, is an R-2R ladder configuration with the three MSBs segmented. Each 2R leg of the ladder is either switched to IOUT1 or the IOUT2 terminal. The IOUT1 terminal of the DAC is held at a virtual GND potential by the use of an external I/V converter op amp. The R-2R ladder is connected to an external reference input VREF that determines the DAC full-scale current. The R-2R ladder presents a code independent load impedance to the external reference of 10kΩ  ±20%. The external reference voltage can vary over a range of –15V to +15V, thus providing bipolar IOUT current operation. By using an external I/V converter and the DAC7811 RFB resistor, output voltage ranges of –VREF to VREF can be generated.

DAC7811 toc_eq_dac_bas337.gifFigure 25. Equivalent R-2R DAC Circuit

When using an external I/V converter and the DAC7811 RFB resistor, the DAC output voltage is given by Equation 1:

Equation 1. DAC7811 q_vovref_bas337.gif

Each DAC code determines the 2R leg switch position to either GND or IOUT. Because the DAC output impedance as seen looking into the IOUT1 terminal changes versus code, the external I/V converter noise gain will also change. Because of this, the external I/V converter op amp must have a sufficiently low offset voltage such that the amplifier offset is not modulated by the DAC IOUT1 terminal impedance change. External op amps with large offset voltages can produce INL errors in the transfer function of the DAC7811 due to offset modulation versus DAC code.

For best linearity performance of the DAC7811, a low offset voltage op amp (such as the OPA277) is recommended (see Figure 26). This circuit allows VREF swinging from –10 V to 10 V.

DAC7811 too_vo_bas337.gifFigure 26. Voltage Output Configuration