SNOS674J October   1997  – September 2024 LMC6482 , LMC6484

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information LMC6482
    5. 5.5 Thermal Information LMC6484
    6. 5.6 Electrical Characteristics: VS = 5V
    7. 5.7 Electrical Characteristics: VS = 3V
    8. 5.8 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Amplifier Topology
      2. 6.3.2 Input Common-Mode Voltage Range
      3. 6.3.3 Rail-to-Rail Output
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Upgrading Applications
      2. 7.1.2 Data Acquisition Systems
      3. 7.1.3 Instrumentation Circuits
    2. 7.2 Typical Applications
      1. 7.2.1 3V Single-Supply Buffer Circuit
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Capacitive Load Compensation
          2. 7.2.1.2.2 Capacitive Load Tolerance
          3. 7.2.1.2.3 Compensating For Input Capacitance
          4. 7.2.1.2.4 Offset Voltage Adjustment
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Typical Single-Supply Applications
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
        1. 8.1.1.1 Spice Macromodel
        2. 8.1.1.2 PSpice® for TI
        3. 8.1.1.3 TINA-TI™ Simulation Software (Free Download)
        4. 8.1.1.4 DIP-Adapter-EVM
        5. 8.1.1.5 DIYAMP-EVM
        6. 8.1.1.6 TI Reference Designs
        7. 8.1.1.7 Analog Filter Designer
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.2.2 Typical Single-Supply Applications

The circuit in Figure 7-17 uses a single supply to half-wave rectify a sinusoid centered about ground. Ri limits current into the amplifier caused by the input voltage exceeding the supply voltage. Full-wave rectification is provided by the circuit in Figure 7-19.

LMC6482 LMC6484 Half-Wave Rectifier With Input Current Protection (Ri)Figure 7-17 Half-Wave Rectifier With Input Current Protection (Ri)
LMC6482 LMC6484 Half-Wave Rectifier WaveformFigure 7-18 Half-Wave Rectifier Waveform

In Figure 7-23, dielectric absorption and leakage is minimized by using a polystyrene or polyethylene hold capacitor. The droop rate is primarily determined by the value of CHOLD and diode leakage current. The ultra-low input current of the LMC648x has a negligible effect on droop. For applications requiring ultra-low input bias current, see the OPA928.

LMC6482 LMC6484 Full-Wave Rectifier With Input Current Protection (RI)Figure 7-19 Full-Wave Rectifier With Input Current Protection (RI)
LMC6482 LMC6484 Large Compliance Range Current SourceFigure 7-21 Large Compliance Range Current Source
LMC6482 LMC6484 Low-Voltage Peak Detector With Rail-To-Rail Peak Capture RangeFigure 7-23 Low-Voltage Peak Detector With Rail-To-Rail Peak Capture Range
LMC6482 LMC6484 Full-Wave Rectifier WaveformFigure 7-20 Full-Wave Rectifier Waveform
LMC6482 LMC6484 Positive Supply Current SenseFigure 7-22 Positive Supply Current Sense

The high CMRR (82dB) of the LMC648x allows excellent accuracy throughout the rail-to-rail dynamic capture range of the circuit.

LMC6482 LMC6484 Rail-to-Rail Sample-and-Hold Circuit Figure 7-24 Rail-to-Rail Sample-and-Hold Circuit

The low-pass filter circuit in Figure 7-25 can be used as an anti-aliasing filter with the same voltage supply as the ADC.

Filter designs can also take advantage of the LMC648x ultra-low input current. The ultra-low input current yields negligible offset error even when large value resistors are used. This in turn allows the use of smaller valued capacitors that take less board space and cost less.

LMC6482 LMC6484 Rail-to-Rail, Single-Supply Low-Pass Filter Figure 7-25 Rail-to-Rail, Single-Supply Low-Pass Filter
Equation 3. R 1 = R 2 ,   C 1 = C 2 ,   f = 1 2 π R 1 C 1 ,   D F = 1 2 C 2 C 1 R 2 R 1