SBOS562G August   2011  – June 2020 INA826

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      General-Purpose Instrumentation Amplifier
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Inside the INA826
      2. 8.3.2  Setting the Gain
        1. 8.3.2.1 Gain Drift
      3. 8.3.3  Offset Trimming
      4. 8.3.4  Input Common-Mode Range
      5. 8.3.5  Input Protection
      6. 8.3.6  Input Bias Current Return Path
      7. 8.3.7  Reference Terminal
      8. 8.3.8  Dynamic Performance
      9. 8.3.9  Operating Voltage
        1. 8.3.9.1 Low-Voltage Operation
      10. 8.3.10 Error Sources
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
    3. 9.3 System Examples
      1. 9.3.1 Circuit Breaker
      2. 9.3.2 Programmable Logic Controller (PLC) Input
      3. 9.3.3 Using TINA-TI SPICE-Based Analog Simulation Program With the INA826
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 CMRR vs Frequency
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

9.2.2 Detailed Design Procedure

There are two modes of operation for the circuit shown in Figure 63: current input and voltage input. This design requires R1 >> R2 >> R3. Given this relationship, the current input mode transfer function is given by Equation 2.

Equation 2. INA826 q_curr_mode_xfer_function_bos562.gif

where

  • G represents the gain of the instrumentation amplifier

The transfer function for the voltage input mode is shown by Equation 3.

Equation 3. INA826 q_voltage_input_mode_xfer_function_bos562.gif

R1 sets the input impedance of the voltage input mode. The minimum typical input impedance is 100 kΩ. This value is selected for R1 because increasing the R1 value also increases noise. The value of R3 must be extremely small compared to R1 and R2. 20 Ω for R3 is selected because that resistance value is much smaller than R1 and yields an input voltage of ±400 mV when operated in current mode (±20 mA).

Equation 4 can be used to calculate R2 given VD = ±400 mV, VIN = ±10 V, and R1 = 100 kΩ.

Equation 4. INA826 q_r2_vd_vin_r1_bos562.gif

The value obtained from Equation 4 is not a standard 0.1% value, so 4.12 kΩ is selected. R1 and R2 also use 0.1% tolerance resistors to minimize error.

The ideal gain of the instrumentation amplifier is calculated with Equation 5.

Equation 5. INA826 q_ideal_gain_bos562.gif

Using the INA826 gain equation, Equation 1, the gain-setting resistor value is calculated as shown by Equation 6.

Equation 6. INA826 q_gain_setting_value_bos562.gif

10.4 kΩ is a standard 0.1% resistor value that can be used in this design. Finally, the output RC filter components are selected to have a –3-dB cutoff frequency of 1 MHz.