SBOS410H June   2007  – June 2016 REF5010 , REF5020 , REF5025 , REF5030 , REF5040 , REF5045 , REF5050

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
  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. Parameter Measurement Information
    1. 8.1 Solder Heat Shift
  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 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
  10. 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
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Power Dissipation
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Documentation
    2. 13.2 Related Links
    3. 13.3 Community Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10 Applications 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.

10.1 Application Information

Data acquisition systems often require stable voltage references to maintain accuracy. The REF50xx family features low noise, very low drift, and high initial accuracy for high-performance data converters. Figure 42 shows the REF5040 in a basic data acquisition system.

10.2 Typical Applications

10.2.1 16-bit, 250-KSPS Data Acquisition System

REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050 cmplt_dt_acq.gif Figure 42. Complete Data Acquisition System Using REF50xx

10.2.1.1 Design Requirements

When using the REF50xx in the design, select a proper output capacitor that does not create gain peaking, thereby increasing total system noise. At the same time, the capacitor must be selected to provide required filtering performance for the system. In addition, input bypass capacitor and noise reduction capacitors must be added for optimum performances. During the design of the data acquisition system, equal consideration must be given to the buffering analog input signal as well as the reference voltage. Having a properly designed input buffer with an associated RC filter is a necessary requirement for good performance of the Data Acquisition System.

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 4 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 bandgap noise of the REF50xx.

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

Table 1. Data Acquisition Measurement Results for Different Conditions

TEST CONDITION 1 TEST CONDITION 2
OPA365 RC filter 124 Ω, 1 nF 124 Ω, 1 nF
REF5040 Output capacitor 10 μF 10 μF + 47 μF
TRIM /NR pin capacitor 0 μF 1 μF
SNR 86.7 dB 92.8 dB

10.2.1.3 Application Curve

REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050 app-curve-1.png Figure 43. FFT plot- Noise floor of Data Acquisition system