SNOS674I October   1997  – February 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 Filter Design Tool
    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

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • D|8
  • P|8
  • DGK|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information
7.2.1.2.3 Compensating For Input Capacitance

The use of large values of feedback resistance with amplifiers that have ultra-low input current, like the LMC648x, is quite common. Large feedback resistors can react with small values of input capacitance due to transducers, photo diodes, and circuits board parasitics to reduce phase margins.

GUID-20231026-SS0I-FPVS-627B-QFHJXJ5FTFSR-low.svg Figure 7-12 Canceling the Effect of Input Capacitance

The effect of input capacitance can be compensated for by adding a feedback capacitor. The feedback capacitor (as in Figure 7-12), Cf, is first estimated by:

Equation 1. 1 2 π R 1 C I N   ≥   1 2 π R 2 C f

or

Equation 2. R1 CIN ≤ R2 Cf

which typically provides significant overcompensation.

Printed-circuit-board stray capacitance can be larger or smaller than that of a bread-board, so the actual optimum value for Cf can be different. Check the value of Cf on the actual circuit. (Refer to the LMC660 quad CMOS amplifier data sheet for a more detailed discussion.)