SBOS748 September   2016 REF6225 , REF6230 , REF6233 , REF6241 , REF6245 , REF6250

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application
      2.      Reference Droop comparison (1 LSB = 19.07 µV, With ADS8881 at 1 MSPS)
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin 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 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Solder Heat Shift
    2. 8.2 Thermal Hysteresis
    3. 8.3 Reference Droop Measurements
    4. 8.4 1/f Noise Performance
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Integrated ADC Drive Buffer
      2. 9.3.2 Temperature Drift
      3. 9.3.3 Load Current
      4. 9.3.4 Stability
    4. 9.4 Device Functional Modes
  10. 10Applications and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Results
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Documentation
    2. 13.2 Related Links
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10.2.2 Detailed Design Procedure

The data acquisition system shown in Figure 53 has three major contributors to the noise and accuracy in the system: the input driver, the reference with driver, and the data converter. Each analog block is carefully designed so that the data converter specifications limit the system specifications. The THS4551, a fully differential operational amplifier is used to drive the 18-bit ADC (ADS8881). The charge-kickback RC filter at the output of the THS4551 is used to reduce the charge kickback created by the opening and closing of the sampling switch inside the ADC. Design the RC filter so that the voltage at the sampling capacitor settles to 18-bit accuracy within the acquisition time of the ADC.

Data-acquisition systems require stable and accurate voltage references in order to perform the most accurate data conversion. The REF62xx family of voltage references have integrated an ADC drive buffer, and can therefore drive the REF pin of the ADS8881 directly, without the need for an external reference buffer. See the Integrated ADC Drive Buffer section for more details about reference-buffer requirements. Correct output capacitor selection for the REF62xx is very important in this design. The Stability section describes the ESR requirements of the output capacitor for stability and burst-mode requirements. A capacitance of 1 μF is connected to the FILT pin to reduce broadband noise of the REF62xx.