SBOS982G June   2020  – July 2022 OPA2863 , OPA4863 , OPA863

PRODMIX  

  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: OPA863
    5. 7.5  Thermal Information: OPA2863
    6. 7.6  Thermal Information: OPA4863
    7. 7.7  Electrical Characteristics: VS = 10 V
    8. 7.8  Electrical Characteristics: VS = 3 V
    9. 7.9  Typical Characteristics: VS = 10 V
    10. 7.10 Typical Characteristics: VS = 3 V
    11. 7.11 Typical Characteristics: VS = 3 V to 10 V
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Input Stage
      2. 8.3.2 Output Stage
        1. 8.3.2.1 Overload Power Limit
      3. 8.3.3 ESD Protection
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-Down Mode
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Low-Side Current Sensing
      1. 9.2.1 Design Requirements
    3. 9.3 Front-End Gain and Filtering
    4. 9.4 Low-Power SAR ADC Driver and Reference Buffer
    5. 9.5 Variable Reference Generator Using MDAC
    6. 9.6 Clamp-On Ultrasonic Flow Meter
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Thermal Considerations
    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

9.4 Low-Power SAR ADC Driver and Reference Buffer

Figure 9-4 shows the use of the OPAx863 devices as a SAR ADC input driver and reference buffer driving the ADS7945. Sensors, which are used for interface with the physical environment, exhibit high output impedance and cannot drive SAR ADC inputs directly. A wide-GBW amplifier like the OPAx863 devices are needed to charge the switching capacitors at the SAR ADC input and to settle fast to the required accuracy within the given acquisition time. The ADC core draws transient current from the reference input during the conversion (digitization) phase, which needs to be driven with a wide-GBW amplifier to offer fast settling and maintain a stable reference voltage for superior digitization performance. The OPAx863 devices reference buffer is used in a composite loop with the OPA378 precision amplifier due to limitations in precision performance of wide-GBW amplifiers. The precision amplifier maintains low-offset output, whereas the OPAx863 devices provide the output drive and fast-settling performance.

Figure 9-4 OPAx863 as Low-Power SAR ADC Driver