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ISOW7741: Expected efficiency with small load

Part Number: ISOW7741
Other Parts Discussed in Thread: ISOW7841, SN6501, ISO7741, SN6505B, ISO6741

Hi,

We are using the ISOW7741 in an isolated circuit that consumes 5 to 10 mA. We noticed that the current drawn by the DC-DC converter is quite high (50 mA). What is the expected efficiency with small load ? There is no efficiency curve in the datasheet. Thanks.

Regards,

Paul

  • Hi Paul,

    Thanks for reaching out and for your interest in ISOW7741.

    The device is in PREVIEW state and is not yet fully released. The datasheet will be updated with all the characteristic curves when the device will be fully released and the status changes to ACTIVE. Meanwhile, you can use ISOW7841 efficiency curve as a close approximation. As specified in the datasheet, ISOW7741 efficiency is going to be slightly lower than ISOW7841 at max load but at smaller loads, we expect them to be very similar. I am copying below the efficiency curve of ISOW7841 for your reference.

    I would also like to point out that, since the device is switching at high frequency (25MHz), the switching losses are going to be a little higher, in general, and at lower output load currents, these switching losses dominate making the efficiency relatively low. From the above curve, the efficiency is estimated to be about 20% at 10mA output load current.

    Let me know if you have any further questions, thanks.


    Regards,
    Koteshwar Rao

  • Hi Koteshwar,

    Thank you very much for this complete answer.

    I think I will switch to another solution: a SN6501 (70% efficiency at 3,3V - 10mA) combined with an ISO7741.

    Best regards,

    Paul

  • Hi Paul,

    Yes, if low load current efficiency is critical then it is better to use SN6501 or SN6505B based solution paired with digital isolator ISO7741 (high-performance) or ISO6741 (optimum performance, lower-cost). Thanks.


    Regards,
    Koteshwar Rao