SNAS809B December   2021  – May 2024 REF35

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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
    6. 6.6 Electrical Characteristics YBH package
    7. 6.7 Typical Characteristics
  8. 7 Parameter Measurement Information
    1. 7.1 Solder Heat Shift
    2. 7.2 Temperature Coefficient
    3. 7.3 Long-Term Stability
    4. 7.4 Thermal Hysteresis
    5. 7.5 Noise Performance
      1. 7.5.1 Low-Frequency (1/f) Noise
      2. 7.5.2 Broadband Noise
    6. 7.6 Power Dissipation
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Supply Voltage
      2. 8.3.2 EN Pin
      3. 8.3.3 NR Pin
    4. 8.4 Device Functional Modes
      1. 8.4.1 Basic Connections
      2. 8.4.2 Start-Up
      3. 8.4.3 Output Transient Behavior
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Negative Reference Voltage
      2. 9.2.2 Precision Power Supply and Reference
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1 Selection of Reference
          2. 9.2.2.2.2 Input and Output Capacitors
          3. 9.2.2.2.3 Selection of ADC
        3. 9.2.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Examples
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.5.1 Low-Frequency (1/f) Noise

Flicker noise, also known as 1/f noise, is a low-frequency noise that affects the device output voltage which can affect precision measurements in ADCs. This noise increases proportionally with output voltage and operating temperature. Noise is measured by filtering the output from 0.1Hz to 10Hz. The 1/f noise is an extremely low value, therefore the frequency of interest must be amplified and band-pass filtered. This is done by using a high-pass filter to block the DC voltage. The resulting noise is then amplified by a gain of 1000. The bandpass filter is created by a series of high-pass and low-pass filter that adds additional gain to make it more visible on a oscilloscope as shown in Figure 7-11. Figure 7-12 shows the effect of flicker noise over 10 second for REF35250. Flicker noise must be tested in a Faraday cage enclosure to block environmental noise.

REF35 Low-Frequency (1/f) Noise Test Setup Figure 7-11 Low-Frequency (1/f) Noise Test Setup
REF35 0.1Hz to 10Hz Voltage Noise Figure 7-12 0.1Hz to 10Hz Voltage Noise

Figure 7-13 shows the typical 1/f noise (0.1Hz to 10Hz) distribution across various load conditions. REF35 device also offers noise reduction functionality by adding an optional capacitor between NR (pin 5) and ground pins.

Figure 7-14 shows the typical 1/f noise (0.1Hz to 10Hz) distribution across REF35 devices with various capacitance between NR pin and GND.

REF35 0.1Hz to 10Hz Noise Distribution vs Load ConditionsFigure 7-13 0.1Hz to 10Hz Noise Distribution vs Load Conditions
REF35 0.1Hz to 10Hz Noise Distribution vs NR CapacitanceFigure 7-14 0.1Hz to 10Hz Noise Distribution vs NR Capacitance