Datasheet REF3425-EP (Texas Instruments) - 10

link to page 10 link to page 10
REF3425-EP , REF3430-EP , REF3433-EP, REF3440-EP
SBAS942B – DECEMBER 2018 – REVISED APRIL 2019
www.ti.com 8 Parameter Measurement Information 8.1 Solder Heat Shift
The materials used in the manufacture of the REF34xx-EP have differing coefficients of thermal expansion, resulting in stress on the device die when the part is heated. 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 four 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 15. The printed circuit board is comprised of FR4 material. The board thickness is 1.65 mm and the area is 114 mm × 152 mm. 300 250 ) 200 (ƒC re tu 150 ra e p m e 100 T 50 0 0 50 100 150 200 250 300 350 400 Time (seconds) C01
Figure 15. Reflow Profile
The reference output voltage is measured before and after the reflow process; the typical shift is displayed in Figure 16. Although all tested units exhibit very low shifts (< 0.01%), higher shifts are also possible depending on the size, thickness, and material of the printed circuit board. An important note is that the histograms 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 second pass to minimize its exposure to thermal stress. 50% 40% (%) 30% ion opulat 20% P 10% 0 0 01 02 -0.02 -0.01 0. 0. D017 Solder Heat Shift (%)
Figure 16. Solder Heat Shift Distribution, VREF (%)
10 Submit Documentation Feedback Copyright © 2018–2019, Texas Instruments Incorporated Product Folder Links: REF3425-EP REF3430-EP REF3433-EP REF3440-EP Document Outline 1 Features 2 Applications 3 Description Table of Contents 4 Revision History 5 Device Comparison Table 6 Pin Configuration and Functions 7 Specifications 7.1 Absolute Maximum Ratings 7.2 ESD Ratings 7.3 Recommended Operating Conditions 7.4 Thermal Information 7.5 Electrical Characteristics 7.6 Typical Characteristics 8 Parameter Measurement Information 8.1 Solder Heat Shift 8.2 Long-Term Stability 8.3 Power Dissipation 8.4 Noise Performance 9 Detailed Description 9.1 Overview 9.2 Functional Block Diagram 9.3 Feature Description 9.3.1 Supply Voltage 9.3.2 Low Temperature Drift 9.3.3 Load Current 9.4 Device Functional Modes 9.4.1  EN Pin 9.4.2 Negative Reference Voltage 10 Application and Implementation 10.1 Application Information 10.2 Typical Application: Basic Voltage Reference Connection 10.2.1 Design Requirements 10.2.2 Detailed Design Procedure 10.2.2.1 Input and Output Capacitors 10.2.2.2 4-Wire Kelvin Connections 10.2.2.3 VIN Slew Rate Considerations 10.2.2.4 Shutdown/Enable Feature 10.2.3 Application Curves 11 Power Supply Recommendations 12 Layout 12.1 Layout Guidelines 12.2 Layout Example 13 Device and Documentation Support 13.1 Documentation Support 13.1.1 Related Documentation 13.2 Related Links 13.3 Receiving Notification of Documentation Updates 13.4 Community Resources 13.5 Trademarks 13.6 Electrostatic Discharge Caution 13.7 Glossary 14 Mechanical, Packaging, and Orderable Information