SBOSAA1H April   2022  – November 2024 OPA2310 , OPA310 , OPA4310

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information for Single Channel
    5. 6.5 Thermal Information for Dual Channel
    6. 6.6 Thermal Information for Quad Channel
    7. 6.7 Electrical Characteristics
    8. 6.8 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Operating Voltage
      2. 7.3.2  Rail-to-Rail Input
      3. 7.3.3  Rail-to-Rail Output
      4. 7.3.4  Capacitive Load and Stability
      5. 7.3.5  Overload Recovery
      6. 7.3.6  EMI Rejection
      7. 7.3.7  ESD and Electrical Overstress
      8. 7.3.8  Input ESD Protection
      9. 7.3.9  Shutdown Function
      10. 7.3.10 Packages with an Exposed Thermal Pad
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 OPAx310 Low-Side, Current Sensing Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4.     Trademarks
    5. 9.4 Electrostatic Discharge Caution
    6. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.4 Capacitive Load and Stability

The OPAx310 is designed to be used in applications where driving a capacitive load is required. As with all operational amplifiers, there can be specific instances where the OPAx310 can become unstable. The particular operational amplifier circuit configuration, layout, gain, and output loading are some of the factors to consider when establishing whether or not an amplifier is stable in operation. An operational amplifier in the unity-gain (1 V/V) buffer configuration that drives a capacitive load exhibits a greater tendency to be unstable than an amplifier operated at a higher noise gain. The capacitive load, in conjunction with the operational amplifier output resistance, creates a pole within the feedback loop that degrades the phase margin. The degradation of the phase margin increases when capacitive loading increases. When operating in the unity-gain configuration, the OPAx310 remains stable with a pure capacitive load up to approximately 75pF with a good phase margin of 40° typical and has no sustained oscillations up to 250pF. The equivalent series resistance (ESR) of some very large capacitors (CL greater than 1μF) is sufficient to alter the phase characteristics in the feedback loop such that the amplifier remains stable. Increasing the amplifier closed-loop gain allows the amplifier to drive increasingly larger capacitance. This increased capability is evident when measuring the overshoot response of the amplifier at higher voltage gains.

One technique for increasing the capacitive load drive capability of the amplifier operating in a unity-gain configuration is to insert a small resistor (typically 10Ω to 20Ω) in series with the output, as shown in Figure 7-3. This resistor significantly reduces the overshoot and ringing associated with large capacitive loads. One possible problem with this technique, however, is that a voltage divider is created with the added series resistor and any resistor connected in parallel with the capacitive load. The voltage divider introduces a gain error at the output that reduces the output swing.

OPA310 OPA2310 OPA4310 Improving Capacitive Load DriveFigure 7-3 Improving Capacitive Load Drive