ZHCSG77F April   2017  – March 2019 INA181 , INA2181 , INA4181


  1. 特性
  2. 应用
  3. 说明
    1.     Device Images
      1.      典型应用电路
  4. 修订历史记录
  5. Device Comparison Table
  6. Pin Configuration and Functions
    1.     Pin Functions: INA181 (Single Channel)
    2.     Pin Functions: INA2181 (Dual Channel) and INA4181 (Quad Channel)
  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
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagrams
    3. 8.3 Feature Description
      1. 8.3.1 High Bandwidth and Slew Rate
      2. 8.3.2 Bidirectional Current Monitoring
      3. 8.3.3 Wide Input Common-Mode Voltage Range
      4. 8.3.4 Precise Low-Side Current Sensing
      5. 8.3.5 Rail-to-Rail Output Swing
    4. 8.4 Device Functional Modes
      1. 8.4.1 Normal Mode
      2. 8.4.2 Unidirectional Mode
      3. 8.4.3 Bidirectional Mode
      4. 8.4.4 Input Differential Overload
      5. 8.4.5 Shutdown Mode
  9. Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Basic Connections
      2. 9.1.2 RSENSE and Device Gain Selection
      3. 9.1.3 Signal Filtering
      4. 9.1.4 Summing Multiple Currents
      5. 9.1.5 Detecting Leakage Currents
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
    1. 10.1 Common-Mode Transients Greater Than 26 V
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12器件和文档支持
    1. 12.1 器件支持
      1. 12.1.1 开发支持
    2. 12.2 文档支持
      1. 12.2.1 相关文档
    3. 12.3 相关链接
    4. 12.4 接收文档更新通知
    5. 12.5 社区资源
    6. 12.6 商标
    7. 12.7 静电放电警告
    8. 12.8 术语表
  13. 13机械、封装和可订购信息


机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)

Signal Filtering

Provided that the INAx181 output is connected to a high impedance input, the best location to filter is at the device output using a simple RC network from OUT to GND. Filtering at the output attenuates high-frequency disturbances in the common-mode voltage, differential input signal, and INAx181 power-supply voltage. If filtering at the output is not possible, or filtering of only the differential input signal is required, it is possible to apply a filter at the input pins of the device. Figure 48 provides an example of how a filter can be used on the input pins of the device.

INA181 INA2181 INA4181 ai_filter_input_pins_bos793.gifFigure 48. Filter at Input Pins

The addition of external series resistance creates an additional error in the measurement; therefore, the value of these series resistors must be kept to 10 Ω (or less, if possible) to reduce impact to accuracy. The internal bias network shown in Figure 48 present at the input pins creates a mismatch in input bias currents when a differential voltage is applied between the input pins. If additional external series filter resistors are added to the circuit, the mismatch in bias currents results in a mismatch of voltage drops across the filter resistors. This mismatch creates a differential error voltage that subtracts from the voltage developed across the shunt resistor. This error results in a voltage at the device input pins that is different than the voltage developed across the shunt resistor. Without the additional series resistance, the mismatch in input bias currents has little effect on device operation. The amount of error these external filter resistors add to the measurement can be calculated using Equation 6, where the gain error factor is calculated using Equation 5.

The amount of variance in the differential voltage present at the device input relative to the voltage developed at the shunt resistor is based both on the external series resistance (RF) value as well as internal input resistor RINT, as shown in Figure 48. The reduction of the shunt voltage reaching the device input pins appears as a gain error when comparing the output voltage relative to the voltage across the shunt resistor. A factor can be calculated to determine the amount of gain error that is introduced by the addition of external series resistance. Calculate the expected deviation from the shunt voltage to what is measured at the device input pins is given using Equation 5:

Equation 5. INA181 INA2181 INA4181 gainerr_factor_bos793.gif


  • RINT is the internal input resistor.
  • RF is the external series resistance.

With the adjustment factor from Equation 5, including the device internal input resistance, this factor varies with each gain version, as shown in Table 1. Each individual device gain error factor is shown in Table 2.

Table 1. Input Resistance

INAx181A1 20 25
INAx181A2 50 10
INAx181A3 100 5
INAx181A4 200 2.5

Table 2. Device Gain Error Factor

INAx181A1 INA181 INA2181 INA4181 gainerr_A1_bos793.gif
INAx181A2 INA181 INA2181 INA4181 gainerr_A2_bos793.gif
INAx181A3 INA181 INA2181 INA4181 gainerr_A3_bos793.gif
INAx181A4 INA181 INA2181 INA4181 gainerr_A4_bos793.gif

The gain error that can be expected from the addition of the external series resistors can then be calculated based on Equation 6:

Equation 6. INA181 INA2181 INA4181 q_gainerror_percent_bas437.gif

For example, using an INA181A2 and the corresponding gain error equation from Table 2, a series resistance of
10 Ω results in a gain error factor of 0.991. The corresponding gain error is then calculated using Equation 6, resulting in an additional gain error of approximately 0.89% solely because of the external 10-Ω series resistors.