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ISOW1432: Heating issue

Rakesh Reddy Yara
Prodigy 30 points
Part Number: ISOW1432


Tool/software:

Dear Team,

We are using the ISOW1432 isolated RS-422 transceiver in our design. When the device is powered on in an idle state (without communication), we observe significant heat dissipation. Do you have any suggestions or recommendations for modifying our design to reduce this heating issue?

Please find the attached schematic capture, where R482 is marked as DNM (Do Not Mount).

Note: The board has already been assembled, so no design changes can be made. Are there any other DNM components or specific resistor values you would recommend to help mitigate the heating issue?

  • 0
    TI__Genius 10010 points

    Hi Rakesh,

    Thank You for reaching out. Please find my inputs below:

    1. Rakesh Reddy Yara said:
      R482 is marked as DNM (Do Not Mount).
    This means that the VISOOUT is set to 5V.
  • To reduce the current consumption in idle state, you can do the following if possible:
    1. Disable internal DC-DC Converter by forcing LOW on EN Pin
    2. Since DE is HIGH in above schematic, the Driver will drive the bus and hence try keeping DE to LOW to reduce the current consumption.
    • Rakesh Reddy Yara said:
      The board has already been assembled, so no design changes can be made. Are there any other DNM components or specific resistor values you would recommend to help mitigate the heating issue?
    Unfortunately, the heating due to DC-DC Converter can not be removed just by adding or removing DNM components. These heat related aspects have to be considered while schematic design and hence provide configurability to DE, /RE, EN/FLT pins so that extra current consumption can be reduced wherever possible.
  • If none of the above suggestions are feasible then you can try adding heat sink. 
  • Also can you quantify the heating here for us to understand if the device is behaving as expected or not.
    • Regards
    Varun