SNAS781E October   2020  – July 2022 REF70

PRODMIX  

  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  REF7012 Electrical Characteristics
    6. 7.6  REF7025 Electrical Characteristics
    7. 7.7  REF7030 Electrical Characteristics
    8. 7.8  REF7033 Electrical Characteristics
    9. 7.9  REF7040 Electrical Characteristics
    10. 7.10 REF7050 Electrical Characteristics
    11. 7.11 Typical Characteristics
  8. Parameter Measurement Information
    1. 8.1 Solder Heat Shift
    2. 8.2 Long-Term Stability
    3. 8.3 Thermal Hysteresis
    4. 8.4 Noise Performance
      1. 8.4.1 1/f Noise
      2. 8.4.2 Broadband Noise
    5. 8.5 Temperature Drift
    6. 8.6 Power Dissipation
  9. Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 EN Pin
    4. 9.4 Device Functional Modes
      1. 9.4.1 Basic Connections
      2. 9.4.2 Negative Reference Voltage
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 Typical Application: Basic Voltage Reference Connection
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1 Input and Output Capacitors
            1. 10.2.1.2.1.1 Application Curve
          2. 10.2.1.2.2 Force and Sense Connection
      2. 10.2.2 Typical Application: DAC Force and Sense Reference Drive Circuit
        1. 10.2.2.1 Design Requirements
  11. 11Power Supply Recommendation
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 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 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

Solder Heat Shift

The materials used in the manufacture of the REF70 have differing coefficients of thermal expansion, resulting in stress on the device die when the part is heated during soldering process. Mechanical and thermal stress on the device die can cause the output voltages to shift, degrading the initial accuracy specifications of the product. Reflow soldering is a common cause of this error. In order to illustrate this effect, a total of 32 devices were soldered on two printed circuit boards [16 devices on each printed circuit board (PCB)] using lead-free solder paste and the paste manufacturer suggested reflow profile. The reflow profile is as shown in Figure 8-1. The printed circuit board is comprised of FR4 material. The board thickness is 1.65 mm and the area is 114 mm × 152 mm.

For recommended reflow profiles using 'Sn-Pb Eutectic Assembly' or 'Pb-Free Assembly' please refer JEDEC J-STD-020 standard.

GUID-B3BBF53B-4F2B-43C8-A2EB-23FF6B08E478-low.png Figure 8-1 Reflow Profile

The reference output voltage is measured before and after the reflow process. Although all tested units exhibit very low shifts, higher shifts are also possible depending on the size, thickness, and material of the printed circuit board. An important note is that the Figure 8-2 display the typical shift for exposure to a single reflow profile. Exposure to multiple reflows, as is common on PCBs with surface-mount components on both sides, causes additional shifts in the output bias voltage. If the PCB is exposed to multiple reflows, the device must be soldered in the last pass to minimize its exposure to thermal stress.

Figure 8-2 Solder Shift