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AD8116 video switch analog input protection

Question asked by dblaker on Jan 17, 2014
Latest reply on Jan 24, 2014 by jpearson

Is there any reason not to add some series resistance (100 ohm to 1kohm) between the termination and the IC video input? 

 

The input has ESD diodes but if there was a mis-wiring or floating ground, etc, the input could see 6 or 12V with enough current to damage the chip.  I recently saw this failure on a design using another manufacturer's switch.  One bad input caused the entire chip and so the entire piece of equipment to fail.  It seems like it would be very easy to damage the chip.

 

The input is listed as >1Mohm input resistance with a <5 uA bias current.  So that is negligible compared to the added series resistor.  The parasitic capacitance may cause a little high frequency loss but that is manageable and easy to estimate.  The termination is close to the IC, so I won't have trace impedance discontinuities of any appreciable length.

   

So it seems easy to protect it but I want to know if I'm missing something?  I don't see this in the AD8116 datasheet or any of the other newer parts.

 

See attached sketch.

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