SBOS632 September 2015 INA188

UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA. 

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1Absolute Maximum Ratings
    2. 6.2ESD Ratings
    3. 6.3Recommended Operating Conditions
    4. 6.4Thermal Information
    5. 6.5Electrical Characteristics: VS = ±4 V to ±18 V (VS = 8 V to 36 V)
    6. 6.6Electrical Characteristics: VS = ±2 V to < ±4 V (VS = 4 V to < 8 V)
    7. 6.7Typical Characteristics
  7. Detailed Description
    1. 7.1Overview
    2. 7.2Functional Block Diagram
    3. 7.3Feature Description
      1. 7.3.1Inside the INA188
      2. 7.3.2Setting the Gain
        1. 7.3.2.1Gain Drift
      3. 7.3.3Zero Drift Topology
        1. 7.3.3.1Internal Offset Correction
        2. 7.3.3.2Noise Performance
        3. 7.3.3.3Input Bias Current Clock Feedthrough
      4. 7.3.4 EMI Rejection
      5. 7.3.5Input Protection and Electrical Overstress
      6. 7.3.6Input Common-Mode Range
    4. 7.4Device Functional Modes
      1. 7.4.1Single-Supply Operation
      2. 7.4.2Offset Trimming
      3. 7.4.3Input Bias Current Return Path
      4. 7.4.4Driving the Reference Pin
      5. 7.4.5Error Sources Example
  8. Application and Implementation
    1. 8.1Application Information
    2. 8.2Typical Application
      1. 8.2.1Design Requirements
      2. 8.2.2Detailed Design Procedure
      3. 8.2.3Application Curve
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1Layout Guidelines
    2. 10.2Layout Example
  11. 11Device and Documentation Support
    1. 11.1Device Support
      1. 11.1.1Development Support
    2. 11.2Documentation Support
      1. 11.2.1Related Documentation
    3. 11.3Community Resources
    4. 11.4Trademarks
    5. 11.5Electrostatic Discharge Caution
    6. 11.6Glossary
  12. 12Mechanical, Packaging, and Orderable Information

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

The INA188 measures a small differential voltage with a high common-mode voltage developed between the noninverting and inverting input. The low offset drift in conjunction with no 1/f noise makes the INA188 suitable for a wide range of applications. The ability to set the reference pin to adjust the functionality of the output signal offers additional flexibility that is practical for multiple configurations.

8.2 Typical Application

Figure 55 shows the basic connections required for operating the INA188. Applications with noisy or high-impedance power supplies may require decoupling capacitors close to the device pins. The output is referred to the output reference (REF) pin that is normally grounded. The reference pin must be a low-impedance connection to assure good common-mode rejection.

INA188 ai_plc_input_sbos632.gif Figure 55. PLC Input (±10 V, 4 mA to 20 mA)

8.2.1 Design Requirements

For this application, the design requirements are:

  • 4-mA to 20-mA input with less than 20-Ω burden
  • ±20-mA input with less than 20-Ω burden
  • ±10-V input with impedance of approximately 100 kΩ
  • Maximum 4-mA to 20-mA or ±20mA burden voltage equal to ±0.4 V
  • Output range within 0 V to 5 V

8.2.2 Detailed Design Procedure

The following steps must be applied for proper device functionality:

  • For a 4-mA to 20-mA input, the maximum burden of 0.4 V must have a burden resistor equal to 0.4 / 0.02 = 20 Ω.
  • To center the output within the 0-V to 5-V range, VREF must equal 2.5 V.
  • To keep the ±20-mA input linear within 0 V to 5 V, the gain resistor (RG) must be 12.4 kΩ.
  • To keep the ±10-V input within the 0-V to 5-V range, attenuation must be greater than 0.05.
  • A 100-kΩ resistor in series with a 4.87-kΩ resistor provides 0.0466 attenuation of ±10 V, well within the ±2.5-V linear limits.

8.2.3 Application Curve

INA188 D326_SBOS632.gif Figure 56. Plot of PLC Input Transfer Function