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ISOW7741-Q1: How to calculate power dissipation of ISOW7741-Q1

Part Number: ISOW7741-Q1

Hello TI 

Can you provide me the formula how to calculate Isolator ISOW7741-Q1 power consumption of this Chip?

Output load current at VISO5V0_ISO is 30mA


Gaurav Mayekar

  • Ambient temperature 90 Degre C.

  • Hi Gaurav,

    Thanks for reaching out.

    The power consumption of device under various test conditions is listed in the datasheet. Please allow me to make some assumptions on test conditions for your case and provide an example for estimating current consumption.

    1. I see that you are operating VDD and VIO at 5V and have set VISOOUT and VISOIN to 5V.
    2. I am assuming that all channels are operating at 1Mbps speed with a load cap of 15pF on all I/O pins.
      1. In this test condition, the max current consumption of data channels will be 6.3mA at VIO and 7.1mA at VISOIN as shown in datasheet below.
    3. I am assuming the efficiency of the DC/DC converter as 46%.
    4. You have mentioned that the external load on VISOOUT as 30mA.
    5. The total load on VISOOUT can be expressed as, IISOOUT = 30mA + "current at VISOIN" = 30mA + 7.1mA = 37.1mA.
    6. The total current consumption at VDD can be expressed as IDD = IISOOUT / Efficiency = 37.1mA / 0.46 = 81mA.
      1. IDD = IISOUT / Efficiency because VDD = VISOOUT.
    7. Total device current consumption would be, ITOTAL = IDD + "current at VIO" = 81mA + 6.3mA = 87.3mA.

    Please note that the actual current consumption could be slightly different because the actual test conditions could be different from what are assumed. For example, VDD and VISOOUT voltages are assumed as 5V but might be slightly higher or lower in during the test.

    I would also like to mention that datasheet doesn't provide specifications for individual temperature values as that would be impractical. Instead it provides specifications for typical, min and max operating conditions. For calculations, please use worst-case values (min or max depending on parameter) to get worst-case calculations. Thanks.

    Koteshwar Rao