SNAS845 august   2023 REF35-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Device Comparison
  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
    1. 8.1 Solder Heat Shift
    2. 8.2 Temperature Coefficient
    3. 8.3 Long-Term Stability
    4. 8.4 Thermal Hysteresis
    5. 8.5 Noise Performance
      1. 8.5.1 Low-Frequency (1/f) Noise
      2. 8.5.2 Broadband Noise
    6. 8.6 Power Dissipation
  10. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Supply Voltage
      2. 9.3.2 EN Pin
      3. 9.3.3 NR Pin
    4. 9.4 Device Functional Modes
      1. 9.4.1 Basic Connections
      2. 9.4.2 Start-Up
      3. 9.4.3 Output Transient Behavior
  11. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application: Negative Reference Voltage
    3. 10.3 Typical Application: Precision Power Supply and Reference
      1. 10.3.1 Design Requirements
      2. 10.3.2 Detailed Design Procedure
        1. 10.3.2.1 Selection of Reference
        2. 10.3.2.2 Input and Output Capacitors
        3. 10.3.2.3 Selection of ADC
      3. 10.3.3 Application Curves
    4. 10.4 Power Supply Recommendations
    5. 10.5 Layout
      1. 10.5.1 Layout Guidelines
      2. 10.5.2 Layout Examples
  12. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.5.2 Broadband Noise

Broadband noise is a noise that appears at higher frequency compared to 1/f noise. The broadband noise is measured by high-pass filtering the output of the reference device, followed by a gain stage and measuring the result on a spectrum analyzer as shown in Figure 8-11

GUID-20230807-SS0I-9831-DFBN-QRMJGLCH8P6H-low.svg Figure 8-11 Broadband Noise Test Setup

For noise sensitive designs, a low-pass filter can be used to reduce broadband noise output noise levels by removing the high frequency components. When designing a low-pass filter, take special care to make sure the output impedance of the filter does not degrade AC performance. This can occur in RC low-pass filters where a large series resistance can impact the load transients due to output current fluctuations. The REF35-Q1 device also offers noise reduction functionality by adding an optional capacitor between NR (pin 5) and ground pins. Figure 8-12 and Figure 8-13 show the noise spectrum for REF35250 and REF35500 devices respectively across various NR pin capacitance.

GUID-7D746B56-CA90-4E95-BDA4-A45CB426EC1E-low.svgFigure 8-12 Noise Spectrum 10 Hz to 100 kHz (VREF = 2.5 V)
GUID-5C89054B-357E-4AEE-A610-0D84F7778E06-low.svgFigure 8-13 Noise Spectrum 10 Hz to 100 kHz (VREF = 5 V)