ADV7262 flow back current from Sink

Dear Sir,

We use ADV7262 on our system.

ADV7262's TMDS lines are connected to the sink which have pull up resistors to 3.3V.
In this case, sometimes "1.8V power line of ADV7262" is flow back current from Sink.
Therefore our system effect 1.8V line for other LSI.

Does ADV7626 of TX have "the inflow prevention circuit"(reverce current prevention circuit) internally?

if yes, maybe our system sometimes does't work this circuit.
Please advice us this phenomenon and any countermeasure.

Thanks and Best regard,

Parents
  • 0
    •  Analog Employees 
    on Sep 30, 2019 1:23 PM over 1 year ago

    Are you referring to the ADV7282?

  • Dir GuenterL-san,

    Sorry, I typo parts number. This question is ADV7626, two in two out HDMI crosspoint.

    I modified the question again.

    --------------

    We use ADV7626 on our system.

    ADV7626's TMDS lines are connected to the sink which have pull up resistors to 3.3V.
    In this case, sometimes "1.8V power line of ADV7262" is flow back current from Sink.
    Therefore our system effect 1.8V line for other LSI.

    Does ADV7626 of TX have "the inflow prevention circuit"(reverce current prevention circuit) internally?

    if yes, maybe our system sometimes does't work this circuit.
    Please advice us this phenomenon and any countermeasure.

     Thanks and Best regard,

  • +1
    •  Analog Employees 
    on Oct 1, 2019 2:03 PM over 1 year ago in reply to IsshinKida

    I assume you are seeing this condition when the ADV7262 is supposed to be powered off and the sink is still power up.  I think the reverse current is going through the ESD protection circuit.  You can stop the reverse current flow by using DC blocking caps in the TMDS line.

    This is a normal problem when you have 2 circuits, one of which is powered up and the other powered down.  I've heard them call 'sneak paths', 'keep-alive paths' or 'zombie paths'.  ESD protection is often the culprit in this problem.

Reply
  • +1
    •  Analog Employees 
    on Oct 1, 2019 2:03 PM over 1 year ago in reply to IsshinKida

    I assume you are seeing this condition when the ADV7262 is supposed to be powered off and the sink is still power up.  I think the reverse current is going through the ESD protection circuit.  You can stop the reverse current flow by using DC blocking caps in the TMDS line.

    This is a normal problem when you have 2 circuits, one of which is powered up and the other powered down.  I've heard them call 'sneak paths', 'keep-alive paths' or 'zombie paths'.  ESD protection is often the culprit in this problem.

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