JAJSL62 February   2021 INA183

PRODUCTION DATA  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and 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
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Single-Supply Operation from IN+
      2. 8.3.2 Low Gain Error and Offset Voltage
      3. 8.3.3 Low Drift Architecture
    4. 8.4 Device Functional Modes
      1. 8.4.1 Normal Operation
      2. 8.4.2 Unidirectional, High-Side Operation
      3. 8.4.3 Input Differential Overload
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 RSENSE and Device Gain Selection
    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
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 ドキュメントの更新通知を受け取る方法
    3. 12.3 サポート・リソース
    4. 12.4 Trademarks
    5. 12.5 静電気放電に関する注意事項
    6. 12.6 用語集
  13. 13Mechanical, Packaging, and Orderable Information

9.1.1 RSENSE and Device Gain Selection

Choosing the largest possible shunt resistor will maximize the accuracy of any current-sense amplifier. A large sense resistor maximizes the differential input signal for a given amount of current flow and reduces the error contribution of the offset voltage. However, there are practical limits as to how large the current-sense resistor can be in a given application because of the resistor size and maximum allowable power dissipation. Equation 1 gives the maximum value for the current-sense resistor for a given power dissipation budget:

Equation 1. GUID-20200713-CA0I-WCQ9-KM9Q-FKT41H51Q3KF-low.gif

where:

  • PDMAX is the maximum allowable power dissipation in RSENSE.
  • IMAX is the maximum current expected to flow through RSENSE.

An additional limitation on the size of the current-sense resistor and device gain is due to the power-supply voltage at the IN+ pin, and device swing-to-rail limitations. To ensure that the current-sense signal is properly passed to the output, both positive and negative output swing limitations must be examined. Equation 2 provides the maximum values of RSENSE and GAIN to keep the device from exceeding the positive swing limitation.

Equation 2. GUID-20200713-CA0I-PPBS-PWFZ-3RHSVCJ5SJNM-low.gif

where:

  • IMAX is the maximum current that will flow through RSENSE.
  • GAIN is the gain of the current-sense amplifier.
  • VSP is the positive output swing as specified in the data sheet.

Positive output swing limitations should be considered when selecting the value of RSENSE. There is always a trade-off between the value of the sense resistor and the gain of the device under consideration. If the sense resistor selected for the maximum power dissipation is too large, then it is possible to select a lower-gain device to avoid positive swing limitations.

The negative swing specification limits how small the sense resistor value can be for a given application. Equation 3 provides the limit on the minimum value of the sense resistor.

Equation 3. GUID-20200713-CA0I-WZZJ-L6Z7-Z55T4XDVG5B4-low.gif

where:

  • IMIN is the minimum current that will flow through RSENSE.
  • GAIN is the gain of the current-sense amplifier.
  • VSN is the negative output swing of the device.