ADuM5402 About Current consumption

Hi,

We are evaluating the ADuM5402.
Please let me ask you a question because it behaved outside the specifications during the experiment.

1. The current consumption of ADuM5402 is recognized as ~ 100mA as shown below.
However, in the experiment, a current of about 250mA (peak) was flowing for about 3.2ms from the time the power was turned on.
Is this normal operation?

2. The current consumption of ADuM5402 tended to increase as the input voltage dropped.
If the input voltage is low (especially at startup / power on), will the current flow more than specified?
In that case, I would like a document that shows the characteristics of the power supply voltage (input) -current consumption of the ADuM5402.

Thank you for your consideration.

Best Regards,

Naohisa

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  • 0
    •  Analog Employees 
    on Nov 19, 2020 9:29 AM 4 months ago

    Hi Naohisa:

    I can not find the content to show "100mA is recognized as the current consumption". please upload it. Right now I can only share some thought based on my understanding about input current. 

    ADuM5402 consists of an isolated DC/DC converter and 4 channel digital isolator. the efficiency of DC/DC converter is around 34%. For a 100mA load condition, the input current is around 290mA. So a 250mA input current is possible. We should figure out the how much load current is applied before we say it is normal operation or not. one thing must be noted that VDD1 and Viso powers digital isolators inside the chip, isolator's bias current on Viso side should be treated as the load current too.

    For a DC/DC converter working in a steady state, it is reasonable to see input current increase with input voltage drop, as Vin * Iin = Vout *Iout / Eff. 

    If you are talking about the power on process, some inrush current can be seen on input side, it is caused by Vout to charge the output capacitor. it will make input current larger than that under steady state. 

    regards

    Chris

  • Hi, Chris

    Thank you for your reply.
    I'm sorry, I forgot.

    The current consumption is described on p.4 "Table 3. DC-to-DC Converter Dynamic Specifications" of the following data sheet.

    Please add the above and give us your opinion.

    https://www.analog.com/media/en/technical-documentation/data-sheets/ADuM5401W_5402W_5403W.pdf#page=4

    Best Regards,

    Naohisa

  • +1
    •  Analog Employees 
    on Nov 20, 2020 8:25 AM 4 months ago in reply to naohisa

    Hi Naohisa:

    Table 3 specify IDD1 when different data rate signal is applied to 4 data channels. It does not mean the maximum IDD1 can appear on ADuM540x. Please refer to Figure 13 on page 17 for more details between input current and load current. 

    In this test, data channel is the only load device for Viso. The current consumption of data channel increase with data rate and load capacitor. 

    Please check if there is any additional load device for Viso beside 4 data channels. 

    Regards

    Chris

Reply
  • +1
    •  Analog Employees 
    on Nov 20, 2020 8:25 AM 4 months ago in reply to naohisa

    Hi Naohisa:

    Table 3 specify IDD1 when different data rate signal is applied to 4 data channels. It does not mean the maximum IDD1 can appear on ADuM540x. Please refer to Figure 13 on page 17 for more details between input current and load current. 

    In this test, data channel is the only load device for Viso. The current consumption of data channel increase with data rate and load capacitor. 

    Please check if there is any additional load device for Viso beside 4 data channels. 

    Regards

    Chris

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