ZHCSV99C February   1997  – October 2024 XTR105

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings #GUID-80F0CD5F-C345-42B2-B6A9-580512790460/R_DESCRIPTION_LI1
    2. 5.2 Recommended Operating Conditions
    3. 5.3 Thermal Information
    4. 5.4 Electrical Characteristics
    5. 5.5 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Linearization
        1. 6.3.1.1 High-Resistance RTDs
      2. 6.3.2 Voltage Regulator
      3. 6.3.3 Open-Circuit Protection
      4. 6.3.4 Reverse-Voltage Protection
      5. 6.3.5 Surge Protection
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 External Transistor
      2. 7.1.2 Loop Power Supply
      3. 7.1.3 2-Wire and 3-Wire RTD Connections
      4. 7.1.4 Radio Frequency Interference
      5. 7.1.5 Error Analysis
    2. 7.2 Typical Applications
    3. 7.3 Layout
      1. 7.3.1 Layout Guidelines
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 接收文档更新通知
    3. 8.3 支持资源
    4. 8.4 Trademarks
    5. 8.5 静电放电警告
    6. 8.6 术语表
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

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7.1.1 External Transistor

Transistor Q1 conducts the majority of the signal-dependent 4-20mA loop current. Using an external transistor isolates the majority of the power dissipation from the precision input and reference circuitry of the XTR105, maintaining excellent accuracy.

The external transistor is inside a feedback loop; therefore, the transistor characteristics are not critical. Requirements are: VCEO = 45V min, β = 40 min, and PD = 800mW. Power dissipation requirements can be lower if the loop power-supply voltage is less than 36V. Some possible choices for Q1 are listed in Figure 7-1.

The XTR105 operates without this external transistor; however, accuracy is somewhat degraded as a result of the internal power dissipation and resulting self-heating. Operation without Q1 is not recommended for extended temperature ranges. A resistor (R = 3.3kΩ) connected between the IRET pin and the E (emitter) pin is advised for operation below 0°C without Q1 to support the full 20mA full-scale output, especially with V+ near 7.5V.

XTR105 Operation Without an External Transistor Figure 7-2 Operation Without an External Transistor