Strange 4066 early death

CHRISKELLY · Posted: Sun Jan 27, 2019 2:34 am Post subject: Strange 4066 early death

Hello people

Somehow I keep damaging 4066 analog switches. Often one or two of the switches will stop opening/closing on command.

I use 100k pullup and pulldown resistors for them.

Aside from normal ic handling mistakes, are there any other things that can cause issues or things that the 4066's don't like?

I've also been using a 4066 to gate this circuit
http://www.runoffgroove.com/tri-vibe.html

Is there anything about the nature of the audio produced here that can inadvertantly damage the 4066?

Cheers
Chris

Steveg · Joined: Apr 23, 2015 Posts: 182 Location: Perth, Australia

Nothing leaps out of the circuit at me. They have the same supply voltage? Signal peak voltage should be no more than .5 volts over the 4066 supply voltage. Signal current should be less than 10 mA ... is that limited by a resistor in any way?

CHRISKELLY · Posted: Sun Jan 27, 2019 6:34 am Post subject:

Thanks for taking a look Steve. Everything sits within those tolerances so I'm guessing it's just a case of sloppy handling!

Steveg · Joined: Apr 23, 2015 Posts: 182 Location: Perth, Australia

Just make sure that nothing is stealing the 4066's supply voltage. That could cause a signal over-voltage condition.

Grumble · Posted: Sun Jan 27, 2019 9:12 am Post subject:

what type of 4066 are you using?
the 74HC4066 uses the ttl logic supply voltages (5 volt) while the 74HCT4066 goes up to 10 volt and CD4066 is cmos compatible (15 volt).

https://assets.nexperia.com/documents/data-sheet/74HC_HCT4066.pdf
http://www.ti.com/lit/ds/symlink/cd4066b.pdf

CHRISKELLY · Posted: Sun Jan 27, 2019 9:57 am Post subject:

Hi Grumble. Ive been using CD4066's.

Went out and bought a fresh batch today and I've been handling them carefully just in case

JovianPyx · Posted: Sun Jan 27, 2019 10:21 am Post subject:

Any chance we can see a full schematic? Without it, we're just guessing.

Things to consider:

All CMOS parts have ESD protection diodes. When those diodes fail, they usually go to short. That will destroy the chip. ESD diode failure happens when any input voltage goes more than one diode voltage below it's Vss pin or one diode voltage above it's Vdd pin

If the voltage across the Vss and Vdd pins is greater than 18 volts for CD4xxx series and 5 volts for 74HCxxxx series, the chip can be destroyed. 74HCxxxx parts might withstand somewhat higher voltage than 5v.

These voltage caveats are true regardless of where the voltage comes from, even an audio signal. All inputs are susceptible, both control inputs and signal inputs.