SBOS945B November   2020  – April 2021 INA849

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and 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 Adjustable Gain Setting
      2. 8.3.2 Gain Drift
      3. 8.3.3 Wide Input Common-Mode Range
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Reference Pin
      2. 9.1.2 Input Bias Current Return Path
      3. 9.1.3 Thermal Effects due to Power Dissipation
    2. 9.2 Typical Application
      1. 9.2.1 Sensor Conditioning Circuit
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
      2. 9.2.2 Phantom Power in Microphone Preamplifier Circuit
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    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

Package Options

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

8.3.1 Adjustable Gain Setting

Figure 8-1 shows that the gain of the INA849 is set by a single external resistor (RG) connected between the RG pins (pins 2 and 3).

GUID-20201008-CA0I-JLH0-S9PG-VF2DQD2KCW12-low.gif Figure 8-1 Simplified Diagram of the INA849 with Output Equation

The value of RG is selected according to the following equation:

Equation 1. GUID-20201008-CA0I-VDZ5-5CZQ-KGMQHLLGWK3H-low.gif

Table 8-1 lists several commonly used gains and resistor values. The 6-kΩ term in Equation 1 is a result of the sum of the two internal 3-kΩ feedback resistors. These on-chip resistors are laser-trimmed to accurate, absolute values. The accuracy and temperature coefficients of these resistors are included in the gain accuracy and drift specifications of the INA849.

Table 8-1 Commonly Used Gains and Resistor Values
DESIRED GAIN (V/V) STANDARD 1% RG (Ω) CALCULATED GAIN (V/V) CALCULATED GAIN ERROR (%)
1 Not connected N/A N/A
2 6.04 k 1.9933 0.33
5 1.50 k 5 0
10 665 10.022 –0.23
20 316 19.987 0.06
50 121 50.586 –1.17
100 60.4 100.337 –0.34
200 30.1 200.335 –0.17
500 12.1 496.867 0.63
1000 6.04 994.377 0.56

The 5-kΩ feedback resistors in the output stage are ratiometrically matched to achieve unity-gain stability. These resistors may shift up to 15% depending on production.

As shown in Figure 8-1 and explained in more detail in Figure 11-1, make sure to connect low-ESR, 0.1-µF, ceramic bypass capacitors between each supply pin and ground, placed as close to the device as possible.