Capacitive Touch Toggle Switch AT42QT1012

[dteck]

Hi everyone,

I'm having a bit of a problem with what I thought was a simple enough design. I was trying to make a on/off toggle switch using the Atmel qt1012 touch sensor. I did a quick layout of a board and used OSH Park to get it made. Everything seemed fine. I put one together and it seemed to work You would touch the "pad" pin and the LED output indicator would light up and the NMOS would conduct. And then in my stupidity I fed it too much voltage. The max rating it 6.5v and I had ramped it up to 12v  That was just a careless mistake on my part. I put the board away and didn't think about it for a while.
Yesterday I pulled one out and planned to use it as part of another project. I just wanted a nice on/off switch for a 5v project. I soldered all the components on and got nothing. or so I thought. When I gave it 5v the QT1012 got super hot. So I thought maybe I shorted something out. So I double and triple check my soldering look for bridges and shorts, use a multimeter and check continuity etc. desolderd and resoldered the chip. Give it 5v again and still no output but overheats like crazy. So I say fine maybe its a bad chip, maybe I overheated it in soldering, whatever. I decided Ill swap it out for my last qt1012. I put that one on the board and it does nothing. It doesn't overheat but it also doesn't do anything at all. 
I used a multimeter to check voltages and it was getting 5v. but there was no output, no voltage on the sensing line, nothing. I thought maybe it was because I was using a cheap meter  . So I pulled out a scope. It showed power going into the chip and nothing coming out. nothing on the output and nothing on the sense line.

I guess its possible I got some bad chips but I was hoping I could ask you guys to look over my design and tell me if I'm doing something stupid that is destroying these chips. 

Datasheet for the qt1012 (AT42QT1012-TSHRCT-ND)
http://www.atmel.com/Images/Atmel-9543-AT42-QTouch-BSW-AT42QT1012_Datasheet.pdf
Datasheet for the nmos (785-1581-1-ND)
http://aosmd.com/res/data_sheets/AON7410.pdf

[Fredled]

The AT42QT1012 is a very unreliable piece of crap.
First of all, it works only in 3V, not in 5V as written in the datasheet.

It's also hyper sensitive to interferences, changes in the environement. very difficult to set up.
Two or more devices on the same PCB won't work reliably.