Problem with a Buffer Gate

[johnnyfp]

Hi,

I've got a SN74AHC1G125 Single Bus Buffer gate, and am at a loss why it's failing.

I've got the buffer on the Dataout of a SPI slave (a CC3000 which does not release its DOUT so needs a buffer), and is enabled when the CS of the device is low, But what I'm seeing on the oscilloscope is in the first picture, The blue line is the output from the buffer, Purple is the input, then after a while I get the second picture, which is only a few hundred millivolts. It seems that the chip is either burning out or something else is going on, I can't seem to understand why it's happening.

Current supply is 3.3v and all I have on the Y pin of the Buffer is the MCU, a SD Card Socket, Not Populated with a card. I measure the Supply at the time and cannot see any spikes or brownouts during the transfer.

Any Ideas at what I should look at next?

[T3sl4co1l]

You didn't stick 0.02uF on there by accident, by any chance...?!

What does the pin do with nothing connected at all?  Scope the supply pin?  Verify the ground is actually grounded?  Any bounce on /CS?

Tim

[johnnyfp]

No Capactior on the output, Both power and ground seem sound. No voltage drop on the Vin of the 74AHC

This Y side of the SPI bus works with the SD Card, just when I activate the Wifi's CS does it not work. /CS seems OK for bounces (Purple line).