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ADV7611 Power (Down) sequencing

Question asked by robert42 on Jun 12, 2013
Latest reply on Jun 12, 2013 by GuenterL

Hello

 

  The ADV7611 datasheet includes requirements concerning sequencing of 3.3 and 1.8 power supplies.

 

  Though there are ways to control the Power Up sequence to fit the requirement (3.3 always `above' 1.8)

  it is not that easy for Powert Down.

 

  Could you please clarify this requirement in more detail ?

     (especially but not only for Power Down)

 

  What are the consequences when violiating this requirement ?

    -) a parasitic diode will conduct current from 1.8 to 3.3 ?

    -) which might destroy the chip, if X mA is conducted for more than Y ms ?

    -) latch up will occur, and might prohibit another startup for Z ms ?

   .-) internal startup will fail ?, and can't be forced with #RESET,

         because #RESET is not really a #RESET, but more

        a sort of RESET-Rrequest, which won't always be honoured ?

   -) some fets gate will be stressed and might shift its threshold ?

   -) any other issues ?

 

  Any Ideas how to design a low cost power supply which fullfills this requirement ?

 

Thank You,

   Robert

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