SBOS410K june   2007  – june 2023 REF5010 , REF5020 , REF5025 , REF5030 , REF5040 , REF5045 , REF5050

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
  8. 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
  9. 8 Parameter Measurement Information
  10. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Temperature Monitoring
      2. 9.3.2 Temperature Drift
      3. 9.3.3 Thermal Hysteresis
      4. 9.3.4 Noise Performance
      5. 9.3.5 Long-Term Stability
      6. 9.3.6 Output Adjustment Using the TRIM/NR Pin
    4. 9.4 Device Functional Modes
      1. 9.4.1 Basic Connections
      2. 9.4.2 Supply Voltage
      3. 9.4.3 Negative Reference Voltage
  11. 10Applications and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 16-Bit, 250-KSPS Data Acquisition System
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
        3. 10.2.1.3 Application Curve
  12. 11Power Supply Recommendations
  13. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Power Dissipation
  14. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Documentation
    2. 13.2 Receiving Notification of Documentation Updates
    3. 13.3 Support Resources
    4. 13.4 Trademarks
    5. 13.5 Glossary
  15. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10.2.1.2 Detailed Design Procedure

The OPA365 is used to drive the 16-bit analog-to-digital converter (ADS8326). The RC filter at the output of the OPA365 is used to reduce the charge kick-back created by the opening and closing of the sampling switch inside the ADC. Design the RC filter such that the voltage at the sampling capacitor settles to 16-bit accuracy within the acquisition time of the ADC. The bandwidth of the driving amplifier must at least be four times the bandwidth of the RC filter.

The REF5040 is used to drive the REF pin of the ADS8326. Proper selection of voltage reference output capacitor is very important for this design. Very low equivalent series resistance (ESR) creates gain-peaking, which degrades SNR of the total system. If the ESR of the capacitor is not enough, then an additional resistor must be added in series with the output capacitor. A capacitance of 1 μF can be connected to the NR pin to reduce band-gap noise of the REF50xx.

SNR measurements using different RC filters at the output of the OPA365, different values of output capacitor for the REF50xx and different values of capacitors at the TRIM/NR pin are shown in Table 10-1.

Table 10-1 Data Acquisition Measurement Results for Different Conditions
TEST CONDITION 1TEST CONDITION 2
OPA365 RC filter124 Ω, 1 nF124 Ω, 1 nF
REF5040 output capacitor10 μF10 μF + 47 μF
TRIM/NR pin capacitor0 μF1 μF
SNR86.7 dB92.8 dB