SBAS438C May   2008  – November 2019 DAC9881

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: AVDD = 5 V
    6. 6.6  Electrical Characteristics: AVDD = 2.7 V
    7. 6.7  Timing Requirements—Standalone Operation Without SDO
    8. 6.8  Timing Requirements—Standalone Operation With SDO and Daisy-Chain Mode
    9. 6.9  Typical Characteristics: AVDD = 5 V
    10. 6.10 Typical Characteristics: AVDD = 2.7 V
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Analog Output
      2. 7.3.2  Reference Inputs
      3. 7.3.3  Output Range
      4. 7.3.4  Input Data Format
      5. 7.3.5  Hardware Reset
      6. 7.3.6  Power-On Reset
        1. 7.3.6.1 Program Reset Value
      7. 7.3.7  Power Down
      8. 7.3.8  Double-Buffered Interface
        1. 7.3.8.1 Load DAC Pin (LDAC)
          1. 7.3.8.1.1 Synchronous Mode
          2. 7.3.8.1.2 Asynchronous Mode
      9. 7.3.9  1.8-V to 5-V Logic Interface
      10. 7.3.10 Power-Supply Sequence
    4. 7.4 Device Functional Modes
      1. 7.4.1 Serial Interface
        1. 7.4.1.1 Input Shift Register
          1. 7.4.1.1.1 Stand-Alone Mode
          2. 7.4.1.1.2 Daisy-Chain Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Bipolar Operation Using the DAC9881
    2. 8.2 Typical Application
      1. 8.2.1 DAC9881 Sample-and-Hold Circuit
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
    3. 8.3 System Example
  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 Support Resources
    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

8.2.1.1 Design Requirements

The inherent architecture of the DAC9881, which consists of an R-2R architecture, enables great performance in regards to noise and accuracy, but at a cost of large glitch area. Glitch area, also known as glitch impulse area, is defined as the area associated with the overshoot or undershoot created by a code transition, and is generally quantified in Volt-seconds. Different code-to-code transitions produce different levels of glitch impulses. DACs with R-2R architectures produce large glitches during major-carry transitions.

There are two methods that can be used to reduce this glitch area:

  1. Add an external RC Filter to the output of the DAC.
    • The low-pass filter helps attenuate high-frequency glitches that would normally propagate to the DAC output. Best practice is to use a small resistor value, as large resistance develops a large potential drop and reduces the voltage seen at the load. Capacitor values can be determined from the desired cutoff frequency of the low-pass filter, as well as settling time.
  2. Another technique is to employ a Sample and Hold (S&H) circuit following the DAC output.
    • In its simplest form, the sample and hold circuit can be constructed from the following components: a capacitive element, output buffer, and switch. A schematic of the simplified S&H is shown in Figure 72.

DAC9881 Simplified_Sample_and_Hold_Circuit.gifFigure 72. Simplified Sample and Hold Circuit