ZHCSJ78 December   2018 INA240-SEP


  1. 特性
  2. 应用
  3. 说明
    1.     Device Images
      1.      典型应用
      2.      增强型 PWM 抑制
  4. 修订历史记录
  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 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Amplifier Input Signal
        1. Enhanced PWM Rejection Operation
        2. Input Signal Bandwidth
      2. 7.3.2 Selecting the Sense Resistor (RSENSE)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Adjusting the Output Midpoint With the Reference Pins
      2. 7.4.2 Reference Pin Connections for Unidirectional Current Measurements
        1. Ground Referenced Output
        2. VS Referenced Output
      3. 7.4.3 Reference Pin Connections for Bidirectional Current Measurements
        1. Output Set to External Reference Voltage
        2. Output Set to Midsupply Voltage
        3. Output Set to Mid-External Reference
        4. Output Set Using Resistor Divider
      4. 7.4.4 Calculating Total Error
        1. Error Sources
        2. Reference Voltage Rejection Ratio Error
          1. Total Error Example 1
          2. Total Error Example 2
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Input Filtering
    2. 8.2 Typical Applications
      1. 8.2.1 Inline Motor Current-Sense Application
        1. Design Requirements
        2. Detailed Design Procedure
        3. Application Curve
      2. 8.2.2 Solenoid Drive Current-Sense Application
        1. Design Requirements
        2. Detailed Design Procedure
        3. Application Curve
    3. 8.3 Do's and Don'ts
      1. 8.3.1 High-Precision Applications
      2. 8.3.2 Kelvin Connection from the Current-Sense Resistor
  9. Power Supply Recommendations
    1. 9.1 Power Supply Decoupling
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Connection to the Current-Sense Resistor
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 接收文档更新通知
    2. 11.2 社区资源
    3. 11.3 商标
    4. 11.4 静电放电警告
    5. 11.5 术语表
  12. 12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)

Input Filtering


Input filters are not required for accurate measurements using the INA240-SEP, and use of filters in this location is not recommended. If filter components are used on the input of the amplifier, follow the guidelines in this section to minimize the effects on performance.

Based strictly on user design requirements, external filtering of the current signal may be desired. The initial location that can be considered for the filter is at the output of the current amplifier. Although placing the filter at the output satisfies the filtering requirements, this location changes the low output impedance measured by any circuitry connected to the output voltage pin. The other location for filter placement is at the current amplifier input pins. This location satisfies the filtering requirement also, however the components must be carefully selected to minimally impact device performance. Figure 29 shows a filter placed at the inputs pins.

INA240-SEP filter-blockdiagram.gifFigure 29. Filter at Input Pins

External series resistance provide a source of additional measurement error, so keep the value of these series resistors to 10 Ω or less to reduce loss of accuracy. The internal bias network shown in Figure 29 creates a mismatch in input bias currents (see Figure 30) when a differential voltage is applied between the input pins. If additional external series filter resistors are added to the circuit, a mismatch is created in the voltage drop across the filter resistors. This voltage is a differential error voltage in the shunt resistor voltage. In addition to the absolute resistor value, mismatch resulting from resistor tolerance can significantly impact the error because this value is calculated based on the actual measured resistance.

INA240-SEP D029_ibpmvdiff_SBOS662.gifFigure 30. Input Bias Current vs Differential Input Voltage

The measurement error expected from the additional external filter resistors can be calculated using Equation 1, where the gain error factor is calculated using Equation 2.

Equation 1. INA240-SEP q_gainerror_percent_bas437.gif

The gain error factor, shown in Equation 1, can be calculated to determine the gain error introduced by the additional external series resistance. Equation 1 calculates the deviation of the shunt voltage resulting from the attenuation and imbalance created by the added external filter resistance. Table 4 provides the gain error factor and gain error for several resistor values.

Equation 2. INA240-SEP input-filter-eq.gif


  • RS is the external filter resistance value

Table 4. Gain Error Factor and Gain Error For External Input Resistors

5 0.998 0.17
10 0.997 0.33
100 0.968 3.23