SBAS738A June   2018  – October 2018 ISO224

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  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  Power Ratings
    6. 7.6  Insulation Specifications
    7. 7.7  Safety-Related Certifications
    8. 7.8  Safety Limiting Values
    9. 7.9  Electrical Characteristics
    10. 7.10 Switching Characteristics
    11. 7.11 Insulation Characteristics Curves
    12. 7.12 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 Analog Input
      2. 8.3.2 Input Clamp Protection Circuit
      3. 8.3.3 Isolation Channel Signal Transmission
      4. 8.3.4 Fail-Safe Output
    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 What to Do and What Not to Do
  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 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

8.3.1 Analog Input

The input stage of the ISO224 feeds a switched capacitor, feed-forward ΔΣ modulator. The modulator converts the analog signal into a bitstream that is transferred over the isolation barrier, as described in the Isolation Channel Signal Transmission section. The high-impedance and low bias-current input of the ISO224 makes the device suitable for isolated voltage sensing applications.

Figure 41 visualizes the difference in the transfer function of the ISO224 depending on the input signal VIN, as specified in the Recommended Operating Conditions table. With the input voltage within the specified full-scale range VFSR, the output of the device changes in a linear way with small error as specified by the nonlinearity parameter in the Electrical Characteristics table. If the input signal exceeds the VFSR range, the nonlinearity of the output signals increases and the amplitude clips at VIN = VCLIPPING.

ISO224 ai_Vin_Vout_bas738.gifFigure 41. Transfer Function of the ISO224

There are two restrictions on the analog input signal at the IN pin. First, if the input voltage VIN exceeds the range of –15 V to 15 V, the current must be limited to 10 mA to prevent damage to the input clamp, see the Input Clamp Protection Circuit section for further information. In addition, the linearity and noise performance of the ISO224 are ensured only when the analog input voltage remains within the specified linear full-scale range (VFSR).