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ISOW7841：About VCC current

user6246671
Prodigy 160 points
Part Number: ISOW7841

Hello experts,

I used ISOW7841 at VCC = 3.3V, VISO = 3.3V and connected 510Ω as a VISO load.

Vcc and VISO are connected to 10uF and 0.1uF respectively.

The Icc at that time is 270 mA with a pulse width of 3 us and repeats in 15 to 25 us cycles.
Is this a normal current waveform?

Best regards,

  • 0
    TI__Mastermind 49495 points

    Hi user62646671,

    Yes, this is expected peak current. If you would like to reduce the peak current then you can either use a series ferrite bead that limits the peak current or reduce output decoupling capacitors from "10uF + 0.1uF" to "3.3uF + 0.1uF". You can also do both of these options which should definitely reduce the input peak current. Let me know the resuojce you try these experiments. Thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 160 points

    Hi, Koteshwar

    Thank you for your reply.

    I would like to check the current when the output decoupling capacitors are reduced.

    In addition, I am thinking of double-insulating SPI communication using two ISOW7841 as shown below. Please tell me the optimum value of the C1-C3 capacitor in this circuit.

    Best regards,

  • 0 in reply to user6246671
    TI__Mastermind 49495 points

    Hi,

    The decoupling capacitors for each ISOW device should be independently provided and also placed within 2mm distance from its power supply pins, Hence, each ISOW7841 device should have 10µF + 0.1µF at VCC and 3.3µF + 0.1µF at VISO. Therefore, you would have to replace C2 with two sets of resistors (10µF + 0.1µF at VCC and 3.3µF + 0.1µF).

    Let me know if you have any other questions, thank you.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 160 points

    Hi, Koteshwar

    Thank you for your reply.

    I would like to check the operation with these recommended capacitors.

    Best regards,