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ISOW7841A-Q1: Regarding Vcc current

Daisuke Higa
Genius 4465 points
Part Number: ISOW7841A-Q1


Tool/software:

Hi support team all.

My customer reported that a large pulse current was observed in the Vcc input current.
Regarding the attached waveform, is this the expected current waveform?
The peak current value is about 280mA.
Also, the cycle is about 17kHz.

Best regards,

Higa

Best regards,

  • 0
    TI__Expert 8730 points

    Hello Higa-San,

    Thanks for reaching out. Please find my inputs below

    This behavior can be expected as the DC-DC Converted demands for higher current during ON period of the internal feedback control loop.

    Few Questions though:

    1. What is the VISO and ISO that device is operating at?
    2. Are the recommended supply(VCC) decoupling capacitors installed on board while capturing this waveform?

    Actual ICC Calculations can also be referred in section 10.2.2 in the Datasheet as well.

    Regards
    Varun

  • 0 in reply to Varun Kumar
    Genius 4465 points

    Hi Varun-san

    Thank you for your reply.

    1. What is the VISO and ISO that device is operating at?

                [ans] Vcc=3V,Viso=3.3V

            2. Are the recommended supply(VCC) decoupling capacitors installed on board while capturing this waveform?

                Vcc side : 10uF+0.1uF (both ceramic)

                Viso side : 10uF+0.1uF (both ceramic)

    Best regards,

    Higa

  • +1 in reply to Daisuke Higa
    TI__Expert 8730 points

    Hi Higa-San,

    Thanks for the inputs. 

    I already said above that this can be expected in a DC-DC Converter. I would recommend to put a current compliance of minimum 500mA on VCC Supply instrument for this sudden current demands during ON time of the converter.

    Adding higher decoupling capacitors(including 10uF+0.1uF) such as 100uF on VCC side can further reduce spike current demand from the  VCC supply.

    Regards
    Varun

  • 0 in reply to Varun Kumar
    Genius 4465 points

    Hi Varun-san

    Thanks!

    I understood.

    BR