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ISO1430: ISO1430 power dissipation

Sammi Shang
Expert 4450 points
Part Number: ISO1430

Dear team,

I see the power dissipation in datasheet 8.5 about ISO1430 when IC was communication. Customer measured the total power assumption with 24 ICs about 600mW @ 3.3V. And it has no much difference whether it was communication. So customer want you help confirm what is the difference of the power assumption when not communication.

Thanks.

Best regards,

Sammi

  • 0
    TI__Mastermind 49495 points

    Hi Sammi,

    Thank you for reaching out. The power dissipation values that you see in the Power Ratings table of section 8.5 of ISO1430 datasheet are the maximum power dissipation values that the device is rated to accept under worst operating conditions.

    You have mentioned that customer is using 24 ICs and the total power dissipated in all of 24 ICs is 600mW @ 3.3V and you do not see any difference whether there is communication or not, the power dissipation remains the same. To make sure customer is following the correct approach to calculate power dissipation in IC, please see the below information.

    The best way to make power dissipation calculations is to use ICC1 and ICC2 values from sections 8.11 and 8.12 of ISO1430 datasheet. Looking at 600mW of total power dissipation for all of 24 ICs, it seems like customer didn't have a termination resistor connected on A-B bus pins. If this is the case then 600mW @ 3.3V seems like a possibly correct value. When customer connects load on A-B pins, he will see much higher current consumption values similar to what is mentioned in sections with 8.11 and 8.12.

    When a load is connected to A-B pins, it is important to note that most of the power gets dissipated in load resistor and only the rest gets dissipated in ISO1430. Hence, total PD can be expressed as below,

    PD = PD1 + PD2
    where PD1 = VCC1 * ICC1 and PD2 = (VCC2-VOD) * ICC2.

    Regarding power dissipation with or without communication, please note that ICC2 value (which is a major contributor for PD) remains somewhat the same whether there is data transmission or not when there is no load connected to A-B. This is probably the reason customer is not seeing much of difference PD with or without communication.
    When there is a load connected to A-B pins, then ICC2 mostly remains high whether continuous data is transmitted or not as long as driver is enabled. Only disabling the driver makes ICC2 value come down. Please refer section 8.12 of datasheet for more details.

    Please do also share customer test conditions and how customer measured 600mW of PD so that I can comment better, thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Mastermind 49495 points

    Hi Sammi,

    Please do let me know if customer was able to consider my inputs and test their power dissipation values. If they did, please do let me know the results. Thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Mastermind 49495 points

    Hi Sammi,

    I hope your questions are answered and customer is able to do power dissipation measurements correctly. I will go ahead and close this E2E post. If you do have any further questions, please do respond to this post or create a new one. Thanks.

    Regards,
    Koteshwar Rao