SLAS411D November   2004  – February 2016 DAC8811

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
    7. 7.7 Typical Characteristics: VDD = 5 V
    8. 7.8 Typical Characteristics: VDD = 2.7 V
  8. 8  Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Stability Circuit
      2. 8.3.2 Positive Voltage Output Circuit
      3. 8.3.3 Bipolar Output Circuit
      4. 8.3.4 Programmable Current Source Circuit
    4. 8.4 Device Functional Mode
    5. 8.5 Programming
      1. 8.5.1 DAC8811 Input Shift Register
  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 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

9.1 Application Information

This design features the DAC8811 followed by a four-quadrant circuit for multiplying DACs. The circuit conditions the current output of an MDAC into a symmetrical bipolar voltage. The design uses an operational amplifier in a transimpedance configuration to convert the MDAC current into a voltage followed by an additional amplifier in a summing configuration to apply an offset voltage.

9.2 Typical Application

DAC8811 typical_application_SLAC411.gif Figure 26. Typical Application

9.2.1 Design Requirements

Using a multiplying DAC requires a transimpedance stage with an amplifier with minimal input offset voltage. The tolerance of the external resistors will vary depending on the goals of the application, but for optimal performance with the DAC8811 the tolerance should be 0.1 % for all of the external resistors. The summing stage amplifier also needs low input-offset voltage and enough slew rate for the output range desired.

9.2.2 Detailed Design Procedure

The first stage of the design converts the current output of the MDAC (IOUT) to a voltage (VOUT) using an amplifier in a transimpedance configuration. A typical MDAC features an on-chip feedback resistor sized appropriately to match the ratio of the resistor values used in the DAC R-2R ladder. This resistor is available using the input shown in Figure 26 called RFB on the MDAC. The MDAC reference and the output of the transimpedance stage are then connected to the inverting input of the amplifier in the summing stage to produce the output that is defined by Equation 5.

Equation 5. DAC8811 equation1_SLAC411.gif

9.2.3 Application Curves

Figure 27 shows the output voltage vs code of this design, while Figure 28 shows the output error vs code. Keep in mind that the error gets worse as the output code increases because the contribution of the gain error increases with code.

DAC8811 D001_SLAS411.gif
Figure 27. Output Voltage vs Input Code
DAC8811 D002_SLAS411.gif
Figure 28. Output Current vs Input Code