SBOS401C July   2007  – April 2016 INA270A-Q1 , INA271A-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  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 Output Voltage Range
    4. 8.4 Device Functional Modes
      1. 8.4.1 First- or Second-Order Filtering
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Basic Connection
      2. 9.1.2 Selecting RS
      3. 9.1.3 Accuracy Variations as a Result of VSENSE and Common-Mode Voltage
        1. 9.1.3.1 Normal Case 1: VSENSE ≥ 20 mV, VCM ≥ VS
        2. 9.1.3.2 Low VSENSE Case 1: VSENSE < 20 mV, -16 V ≤ VCM < 0; and Low VSENSE Case 3: VSENSE < 20 mV, VS < VCM ≤ 80 V
        3. 9.1.3.3 Low VSENSE Case 2: VSENSE < 20 mV, 0 V ≤ VCM ≤ VS
      4. 9.1.4 Transient Protection
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Shutdown
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 RFI and EMI
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Related Links
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

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11 Layout

11.1 Layout Guidelines

  • Connect the input pins to the sensing resistor using a Kelvin or 4-wire connection. This connection technique ensures that only the current-sensing resistor impedance is detected between the input pins. Poor routing of the current-sensing resistor commonly results in additional resistance present between the input pins. Given the very low ohmic value of the current resistor, any additional high-current carrying impedance can cause significant measurement errors.
  • Place the power-supply bypass capacitor as closely as possible to the supply and ground pins. The recommended value of this bypass capacitor is 0.1 μF. Additional decoupling capacitance can be added to compensate for noisy or high-impedance power supplies.

11.1.1 RFI and EMI

Attention to good layout practices is always recommended. Keep traces short and, when possible, use a printed circuit board (PCB) ground plane with surface-mount components placed as close to the device pins as possible. Small ceramic capacitors placed directly across amplifier inputs can reduce RFI and EMI sensitivity. PCB layout should locate the amplifier as far away as possible from RFI sources. Sources can include other components in the same system as the amplifier itself, such as inductors (particularly switched inductors handling a lot of current and at high frequencies). RFI can generally be identified as a variation in offset voltage or dc signal levels with changes in the interfering RF signal. If the amplifier cannot be located away from sources of radiation, shielding may be needed. Twisting wire input leads makes them more resistant to RF fields. The difference in input pin location of the INA27xA-Q1 versus the INA193 through INA198 may provide different EMI performance.

11.2 Layout Example

INA270A-Q1 INA271A-Q1 ai_recommended_layout_sbos401.gif Figure 23. INA27xA-Q1 Example Layout