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ADG1434 Backfeed to Vdd when powered off

Question asked by JeffD on Oct 10, 2011
Latest reply on Oct 11, 2011 by JeffD

I am using the ADG1434 biased at +15V for Vdd, -15V for Vss. This switch is being used to multiplex RS-232 data (+/-12V single ended).

 

The switch works great when it's powered on, but I am having a problem with it when powered OFF.

 

Here's the scenario:  Vdd = 0V, Vss = 0V and all other pins equal 0V, but there is an external signal being driven into one of the switch inputs (S3B in this case) at 12V. This 12V is being back fed to Vdd (Vdd now = 12V), which goes to several other parts, including 20 other ADG1434 switches. In some cases this voltage is going through Vdd of the other parts and is getting out on S2B and S1B, but this case is never consistent.

 

Any advice on how to keep this from happening?

 

See attached for further detail.

 

Thanks,

 

Jeff

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