JAJSCL0C July   2016  – December 2021 INA240


  1. 特長
  2. アプリケーション
  3. 概要
  4. Revision History
  5. Device Comparison
  6. Pin Configuration and Functions
  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 Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Amplifier Input Signal
        1. Enhanced PWM Rejection Operation
        2. Input Signal Bandwidth
      2. 8.3.2 Selecting the Sense Resistor (RSENSE)
    4. 8.4 Device Functional Modes
      1. 8.4.1 Adjusting the Output Midpoint With the Reference Pins
      2. 8.4.2 Reference Pin Connections for Unidirectional Current Measurements
        1. Ground Referenced Output
        2. VS Referenced Output
      3. 8.4.3 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. 8.4.4 Calculating Total Error
        1. Error Sources
        2. Reference Voltage Rejection Ratio Error
          1. Total Error Example 1
          2. Total Error Example 2
  9. Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Input Filtering
    2. 9.2 Typical Applications
      1. 9.2.1 Inline Motor Current-Sense Application
        1. Design Requirements
        2. Detailed Design Procedure
        3. Application Curve
      2. 9.2.2 Solenoid Drive Current-Sense Application
        1. Design Requirements
        2. Detailed Design Procedure
        3. Application Curve
    3. 9.3 What to Do and What Not to Do
      1. 9.3.1 High-Precision Applications
      2. 9.3.2 Kelvin Connection from the Current-Sense Resistor
  10. 10Power Supply Recommendations
    1. 10.1 Power Supply Decoupling
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Connection to the Current-Sense Resistor
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 サポート・リソース
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information



Input Filtering


Input filters are not required for accurate measurements using the INA240, 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 9-1 shows a filter placed at the inputs pins.

GUID-43013221-653B-4876-97EF-310CD32A719D-low.gifFigure 9-1 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 9-1 creates a mismatch in input bias currents (see Figure 9-2) 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.

GUID-1BA70934-BAB1-4568-8B0E-FF0EF34F11A0-low.gifFigure 9-2 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. GUID-0A092707-4731-4945-B32C-94C91EBFA501-low.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 9-1 provides the gain error factor and gain error for several resistor values.

Equation 2. GUID-53F6D08F-264E-4D54-B198-46E54057D425-low.gif


  • RS is the external filter resistance value
Table 9-1 Gain Error Factor and Gain Error For External Input Resistors