SBOS807E December   2016  – May 2020 OPA187 , OPA2187 , OPA4187

UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      OPAx187 Offers Precision Low-Side Current Measurement Capability
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions: OPA187
    2.     Pin Functions: OPA2187
    3.     Pin Functions: OPA4187
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information: OPA187
    5. 6.5 Thermal Information: OPA2187
    6. 6.6 Thermal Information: OPA4187
    7. 6.7 Electrical Characteristics: High-Voltage Operation
    8. 6.8 Electrical Characteristics: Low-Voltage Operation
    9. 6.9 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Operating Characteristics
      2. 7.3.2 Phase-Reversal Protection
      3. 7.3.3 Input Bias Current Clock Feedthrough
      4. 7.3.4 Internal Offset Correction
      5. 7.3.5 EMI Rejection
      6. 7.3.6 Capacitive Load and Stability
      7. 7.3.7 Electrical Overstress
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 High-Side Voltage-to-Current (V-I) Converter
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
      2. 8.2.2 Discrete INA + Attenuation for ADC With 3.3-V Supply
      3. 8.2.3 Bridge Amplifier
      4. 8.2.4 Low-Side Current Monitor
      5. 8.2.5 Programmable Power Supply
      6. 8.2.6 RTD Amplifier With Linearization
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 TINA-TI™ (Free Software Download)
        2. 11.1.1.2 TI Precision Designs
        3. 11.1.1.3 WEBENCH® Filter Designer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Support Resources
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.1.2 Detailed Design Procedure

The V-I transfer function of the circuit is based on the relationship between the input voltage, VIN, and the three current sensing resistors, RS1, RS2, and RS3. The relationship between VIN and RS1 determines the current that flows through the first stage of the design. The current gain from the first stage to the second stage is based on the relationship between RS2 and RS3.

This application benefits from an operational amplifier with low offset voltage, low temperature drift, and rail-to-rail output. The OPAx187 CMOS operational amplifiers are high-precision, ultra-low offset, ultra-low drift amplifier, optimized for wide-voltage, single-supply operation, with an output swing to within 5 mV of the positive rail. The OPAx187 family uses chopping techniques to provide low initial offset voltage and near-zero drift over time and temperature. Low offset voltage and low drift reduce the offset error in the system, making this device appropriate for precise dc control. The rail-to-rail output stage of the OPAx187 makes sure that the output swing of the operational amplifier is able to fully control the gate of the MOSFET devices within the supply rails.

A detailed error analysis, design procedure, and additional measured results are given in reference design TIPD102, a step-by-step process to design a High-Side Voltage-to-Current (V-I) Converter.

For step-by-step design procedure, circuit schematics, bill of materials, PCB files, simulation results, and test results, refer to TI Precision Design TIPD102, High-Side Voltage-to-Current (V-I) Converter.