SLLSFN5B June   2023  – September 2025 ISO1228

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
    5. 5.5  Power Ratings
    6. 5.6  Insulation Specifications
    7. 5.7  Safety-Related Certifications
    8. 5.8  Safety Limiting Values
    9. 5.9  Electrical Characteristics—DC Specification
    10. 5.10 Switching Characteristics—AC Specification
    11. 5.11 Typical Characteristics
  7. 6 Parameter Measurement Information
    1. 6.1 Test Circuits
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Surge Protection
      2. 7.3.2  Field Side LED Indication
      3. 7.3.3  Serial and Parallel Output option
      4. 7.3.4  Cyclic Redundancy Check (CRC)
      5. 7.3.5  FAULT Indication
      6. 7.3.6  Digital Low Pass Filter
      7. 7.3.7  SPI Register Map
      8. 7.3.8  SPI Timing - Non-Daisy Chain
      9. 7.3.9  SPI Timing - Daisy Chain
      10. 7.3.10 SPI Timing - Burst Mode
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Sinking Type Digital Inputs
      2. 8.2.2 Sourcing Type Digital Inputs
      3. 8.2.3 Sink/Source Type Digital Inputs
      4. 8.2.4 Design Requirements
        1. 8.2.4.1 Detailed Design Procedure
          1. 8.2.4.1.1 Current Limit
          2. 8.2.4.1.2 Voltage Thresholds
          3. 8.2.4.1.3 Wire-Break Detection
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information
8.2.4.1.1 Current Limit

The ISO1228 device includes a selectable current limit feature to limit the current drawn from the INx pins. Current limiting prevents input current from increasing linearly with input voltage beyond the voltage high transition threshold, reducing both chip and system power dissipation, and board temperature.

The RILIM and RPAR resistors set the value of the current limit (IL) according to the equation shown below.

Equation 1. IL (typical) = 2.9mA when RILIM = 0kΩ & RPAR = 13kΩ
Equation 2. IL (typical) = 3.9mA when RILIM = 1kΩ & RPAR = 9.76kΩ.

A 1% tolerance is recommended on RPAR but 5% tolerance can also be used if a higher variation in the current limit value is acceptable. CFIL value is set to 1nF when RILIM = 1kΩ. The value of RPAR is the same for all channels and is required to achieve the correct current limit behavior.