SBOS792A August   2017  – January 2018 INA828

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      INA828 Simplified Internal Schematic
      2.      Typical Distribution of Input Offset Voltage Drift
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Setting the Gain
        1. 7.3.1.1 Gain Drift
      2. 7.3.2 EMI Rejection
        1. Table 2. INA828 EMIRR for Frequencies of Interest
      3. 7.3.3 Input Common-Mode Range
      4. 7.3.4 Input Protection
      5. 7.3.5 Operating Voltage
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Reference Terminal
    2. 8.2 Input Bias Current Return Path
    3. 8.3 PCB Assembly Effects on Precision
    4. 8.4 Typical Application
      1. 8.4.1 Design Requirements
      2. 8.4.2 Detailed Design Procedure
      3. 8.4.3 Application Curves
    5. 8.5 Other Application Examples
      1. 8.5.1 Resistance Temperature Detector Interface
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2 Input Bias Current Return Path

The input impedance of the INA828 is extremely high—approximately 100 GΩ. However, a path must be provided for the input bias current of both inputs. This input bias current is typically 150 pA. High input impedance means that this input bias current changes very little with varying input voltage.

Input circuitry must provide a path for this input bias current for proper operation. Figure 64 shows various provisions for an input bias current path. Without a bias current path, the inputs float to a potential that exceeds the common-mode range of the INA828, and the input amplifiers saturate. If the differential source resistance is low, the bias current return path can be connected to one input (as shown in the thermocouple example in Figure 64). With a higher source impedance, using two equal resistors provides a balanced input with possible advantages of a lower input offset voltage as a result of bias current and better high-frequency common-mode rejection.

INA828 ai_in_cm_path_bos770.gifFigure 64. Providing an Input Common-Mode Current Path