ADuM5402, state of logic output when power is not well supplied

Hi,

We are assuming what would be occured when power supply from primaly side is stopped by any reason during operation, for example, malfunction at internal or external circuitry, at ADuM5402.

In this case, how is the state of primary/secondary side of output pins supposed to be ?

 

Subject to page.24 of datasheet, POWER CONSIDERATIONS, we are assuming output become to be high-impedance, but it can allow to understood that it may be default low, or remain state just before power down.

Especially following last phrase are not clear to see...<The outputs on the secondary side hold the last state that they received from the primary side. Either the UVLO level is reached and the outputs are placed in their high impedance state, or the outputs detect a lack of activity from the primary side inputs and the outputs are set to their default low value before the secondary power reaches UVLO.>

If you provide another explain by focusing a case power supply suddenly stop during normal operation, it would be very much appreciated.

Best Regards,

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  • 0
    •  Analog Employees 
    on May 15, 2013 5:54 PM over 7 years ago

    Hello Usaghi

    The table is largely correct, except where there is data present on a side that is supposed to be unpowered.  A digital input can provide enough current to allow the part to try to operate so some of the cases where data is present on an input and the power supply is off may try to send data across the barrier and you will get indeterminate operation.  That side of the part could be turning on and off in an uncontrolled way.  The only way to get completely determined behavior is to be sure that the data signals from other devices are off as well as the loacl power.

    on on output: Result at Vox rec output: Result at Vox Primary side Secondary side tion
    Power supply Power supply Primary side input: data at Vix Di Secondary side input: data at Vix
    No No input no data => output Z
    input data exist => output Indeterminate
    output Z <= input no data
    output Z <= input data exist
    No Yes input no data => output L
    input data exist => output Indeterminate
    output Z <= input no data
    output Z <= input data exist
    Assume isopower disabled to do this, Yes No input no data => output Z
    input data exist => output Z
    output L <= input no data
    output Indeterminate <= input data exist
    Z : High-impedance ,
    L : logic Low

    Best regards,

    MSCantrell

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  • 0
    •  Analog Employees 
    on May 15, 2013 5:54 PM over 7 years ago

    Hello Usaghi

    The table is largely correct, except where there is data present on a side that is supposed to be unpowered.  A digital input can provide enough current to allow the part to try to operate so some of the cases where data is present on an input and the power supply is off may try to send data across the barrier and you will get indeterminate operation.  That side of the part could be turning on and off in an uncontrolled way.  The only way to get completely determined behavior is to be sure that the data signals from other devices are off as well as the loacl power.

    on on output: Result at Vox rec output: Result at Vox Primary side Secondary side tion
    Power supply Power supply Primary side input: data at Vix Di Secondary side input: data at Vix
    No No input no data => output Z
    input data exist => output Indeterminate
    output Z <= input no data
    output Z <= input data exist
    No Yes input no data => output L
    input data exist => output Indeterminate
    output Z <= input no data
    output Z <= input data exist
    Assume isopower disabled to do this, Yes No input no data => output Z
    input data exist => output Z
    output L <= input no data
    output Indeterminate <= input data exist
    Z : High-impedance ,
    L : logic Low

    Best regards,

    MSCantrell

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