ZHCSJM1A April   2019  – June 2019 INA818

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      INA818 简化内部原理图
      2.      输入阶段失调电压漂移的典型分布
  4. 4 修订历史记录
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 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: Table of Graphs
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Setting the Gain
        1. 8.3.1.1 Gain Drift
      2. 8.3.2 EMI Rejection
      3. 8.3.3 Input Common-Mode Range
      4. 8.3.4 Input Protection
      5. 8.3.5 Operating Voltage
      6. 8.3.6 Error Sources
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Reference Pin
      2. 9.1.2 Input Bias Current Return Path
    2. 9.2 Typical Applications
      1. 9.2.1 Three-Pin Programmable Logic Controller (PLC)
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Resistance Temperature Detector Interface
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12器件和文档支持
    1. 12.1 文档支持
      1. 12.1.1 相关文档
    2. 12.2 接收文档更新通知
    3. 12.3 社区资源
    4. 12.4 商标
    5. 12.5 静电放电警告
    6. 12.6 Glossary
  13. 13机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

9.2.1.2 Detailed Design Procedure

There are two modes of operation for the circuit shown in Figure 69: current input and voltage input. This design requires R1 >> R2 >> R3. Given this relationship, Equation 3 calculates the current input mode transfer function.

Equation 3. INA818 q_curr_mode_xfer_function_bos562.gif

where

  • G represents the gain of the instrumentation amplifier
  • VD represents the differential voltage at the INA818 inputs
  • VREF is the voltage at the INA818 REF pin
  • IIN is the input current

Equation 4 shows the transfer function for the voltage input mode.

Equation 4. INA818 q_voltage_input_mode_xfer_function_bos562.gif

where

  • VIN is the input voltage

R1 sets the input impedance of the voltage input mode. The minimum typical input impedance is 100 kΩ. 100 kΩ is selected for R1 because increasing the R1 value also increases noise. The value of R3 must be extremely small compared to R1 and R2. 20 Ω for R3 is selected because that resistance value is much smaller than R1 and yields an input voltage of ±400 mV when operated in current mode (±20 mA).

Use Equation 5 to calculate R2 given VD = ±400 mV, VIN = ±10 V, and R1 = 100 kΩ.

Equation 5. INA818 q_r2_vd_vin_r1_bos562.gif

The value obtained from Equation 5 is not a standard 0.1% value, so 4.17 kΩ is selected. R1 and R2 also use 0.1% tolerance resistors to minimize error.

Use Equation 6 to calculate the ideal gain of the instrumentation amplifier.

Equation 6. INA818 q_ideal_gain_bos562.gif

Equation 7 calculates the gain-setting resistor value using the INA818 gain equation, Equation 1.

Equation 7. INA818 ai_EQ002_SBOS792.gif

10.5 kΩ is a standard 0.1% resistor value that can be used in this design.