SBVS020C September   2000  β€“ February 2020 REF200

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Functional Block Diagram
  4. Revision History
  5. Pin Configuration and Functions
    1.     Pin Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Electrical Characteristics
    5. 6.5 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Temperature Drift
    4. 7.4 Device Functional Modes
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Lead Resistance Cancelation (3-Wire RTD)
      3. 8.2.3 Application Curves
    3. 8.3 System Examples
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 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
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

Detailed Design Procedure

Figure 12 and Figure 13 shows the schematic of the RTD amplifier for minimum and maximum output conditions. This circuit was designed for a –50°C to 150°C RTD temperature range. At –50°C the RTD resistance is 80.3 Ω and the voltage across it is 8.03 mV (VRTD = (100 μA) (80.3 Ω), see Figure 2). Notice that R3 develops a voltage drop that opposes the RTD drop. The drop across R3 is used to shift amplifiers input differential voltage to a minimum level. The output is the differential input multiplied by the gain (Vout = 698 βˆ™ 160 μV = 0.111 V). At 150°C, the RTD resistance is 148 Ω and the voltage across it is 14. 8 mV (VRTD = (100 μA × 148 Ω ). This produces a differential input of 6.93 mV and an output voltage of 4.84 V (VOUT = 698 βˆ™ 6.93 mV = 4.84 V , see Figure 13). For more detailed design procedures and results, refer to the reference guide, RTD to Voltage Reference Design Using Instrumentation Amplifier and Current Reference (TIDU969).

REF200 RTD_Amplifier_Min_Out.gifFigure 12. RTD Amplifier with Minimum Output Condition
REF200 RTD_Amplifier_Max_Out.gifFigure 13. RTD Amplifier with Maximum Output Condition