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USB disconnect detection: VREGIN staying high

Question asked by Vincent Göbel on Dec 23, 2016
Latest reply on Dec 27, 2016 by xiangjun.rong

Hi all,

i ran into a problem to detect the disconnect of USB on a MK22FN512. 

VREGIN is connected to the output of an external 3.3V voltage regulator (NCP502SQ33T2G). I'm checking the state of that connection over a voltage divider to stay under my 1.8V Supply. The measuring pin is configured as input, no pull.

The reason for not taking the enable pin of the external regulator is that the voltage on this pin may be alot higher.

 

If I disable the voltage regulator the output goes down to about 2.3 volt and stays there instead of going to 0. If i short it the signal goes low and stays low.

I tried adding a pulldown to empty the output capacitor of the regulator but it doesn't help, so there must be some kind of leakage somewhere.

Could there be any feedback from the VREGIN pin? 

Any hints would be great.

 

Happy Holidays

Vincent

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