SLLA529 October   2020 ISO7741

 

  1. 1 Introduction
  2. 2 General Considerations
  3. 3 Group-Isolated Analog Input Modules
    1.     Requirements for Digital Isolator in Group-Isolated AI modules:
    2.     Requirements for Isolated Power in Group-Isolated AI modules:
  4. 4 Channel-to-Channel Isolated Analog Input Modules
    1.     Requirements for Digital Isolator in channel-to-channel isolated AI modules
    2.     Requirements for Isolated Power in channel-to-channel isolated AI modules
  5. 5Isolation Products for Analog Input Modules
  6. 6Conclusion
  7. 7References
    1.     Trademarks

5 Isolation Products for Analog Input Modules

The ISO77xx family of digital isolators (example: ISO7741DBQ, ISO7762DBQ), offer SPI speeds up-to 16 MHz and low power of 2 mA per channel at 10 Mbps, and are suitable for group isolation. Similarly the ISO70xx family of digital isolators (ISO7041DBQ and ISO7021D) offer industry leading low power consumption of 15uA/channel at 100 kHz, and fit the needs for channel to channel isolated analog input modules. Both families offer 3 kVRMS isolation in small 5 mm x 6 mm footprint packages. These devices support level 3 transient immunity per IEC 61000-4-x standards, including +/-8 kV ESD contact discharge.

The SN6505 family of push-pull transformer driver devices creates isolated power supplies with efficiency of 80% to 90% at 5-W full load, and 50% to 60% at light loads. Any output voltage can be generated by choosing the right transformer ratio. The feedforward converter is easy to design and does not need an analog feedback channel. The symmetric push-pull topology is well known to achieve very low emissions due to symmetric operation. The built-in spread spectrum in SN6505 avoids sharp peaks in the emissions profile.