Author Topic: 4066 bilateral switch unused inputs and maximum voltage through switches?  (Read 14057 times)

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Offline dentaku

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I was looking at the 4066b - quad bilateral switch datasheets the On Semi one is clearer as to what pins do what than the TI one I've found.
http://pdf.datasheetcatalog.com/datasheets/320/206765_DS.pdf

I know about tying unused inputs to ground but I'm still wondering what exactly is considered an input in the case of something like the 4066?
I'm assuming it means the four CONTROL inputs but what about the switch INs themselves. Are they inputs that you would connect to ground if they are unused?

ALSO: If I power it with 9V and use square waves for CONTROL I'm assuming I can't run a signal that is adjustable to be anywhere between -9V to +9V through the switch?
because the datasheet says...
"The maximum analog signal level is determined by VDD and VSS. The analog voltage must not swing higher than VDD or lower than VSS."

Basically, I want to use a counter IC of some sort to send pulses to the CONTROL inputs which in turn switches four varying voltages (four voltage dividers) to a VCO's control voltage input. The problem is that to get the maximum range of frequencies from the VCO I need to give it -9V to +9v and I don't think the 4066 can handle this.
« Last Edit: February 24, 2014, 02:41:26 am by dentaku »
 

Offline GK

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #1 on: February 24, 2014, 03:11:40 am »
4066 will do +/-7.5 V max on bipolar supply rails. Look at something from the DG or ADG range to switch higher amplitude analogue signals - eg DG308. These devices also more conveniently reference the logic control inputs to ground when operating on bipolar rails.
« Last Edit: February 24, 2014, 03:18:43 am by GK »
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Offline amyk

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #2 on: February 24, 2014, 12:11:20 pm »
The principle behind what to do with unused inputs is to avoid having a floating gate. The switch inputs don't connect to gates.
 

Offline sync

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #3 on: February 24, 2014, 01:02:39 pm »
Look at the 4051,4052, 4053 analog multiplexer. These will work up to +/-9V or +/-10V (depending on manufacture).
 

Offline dentaku

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #4 on: February 24, 2014, 02:02:56 pm »
Aha... That's what I was expecting so it's nice to see someone here explain it in a simple way like that.

The principle behind what to do with unused inputs is to avoid having a floating gate. The switch inputs don't connect to gates.
 

Offline dentaku

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #5 on: February 24, 2014, 02:15:52 pm »
I DO have a 4051BE and a 4051BP plus a 4052BP and a 4053BE so I guess I have some reading to do :) I got all of these from the collection of an old man who died last year so I'm never exactly sure what I have in my bins.

Basically I'm seeing if I can make a little step sequencer with counters, analogue switches and voltage dividers connected to a VCO control voltage input.
VCOs, VCFs, VCAs are easy enough (LM13700s are nice) but I'm still learning about these old 4000 series ICs.

Look at the 4051,4052, 4053 analog multiplexer. These will work up to +/-9V or +/-10V (depending on manufacture).
« Last Edit: February 24, 2014, 02:20:12 pm by dentaku »
 

Offline edavid

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #6 on: February 24, 2014, 04:51:56 pm »
You should probably put an op amp stage in front of the VCO control input, so it can accept a more convenient voltage range.
 

Offline dentaku

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #7 on: February 24, 2014, 05:04:09 pm »
Yeah. I just might do that.  :-+

You should probably put an op amp stage in front of the VCO control input, so it can accept a more convenient voltage range.
 

Offline edavid

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #8 on: February 24, 2014, 05:43:56 pm »
Where did people get the idea that it's OK to top post?  Is it a mobile thing?
 

Offline GK

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #9 on: February 24, 2014, 10:58:42 pm »
Maximum "nominal" supply voltage for the 4000 series is 15V. You can push it by running them at the absolute maximum ratings, but that generally isn't a very good design practice.

Unless you are using rail-rail in/out op-amps, they will need at least a volt or two of headroom, so you won't be able to power them from the same rail potentials as the analogue switches, if you intend to run the 4000-series analogue switches to their limits. The DGXXX series on the other hand can run on rails up to +/-22V, so they can be powered directly from the op-amp supply rails. That's generally a lot more convenient.
 
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Offline edavid

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #10 on: February 25, 2014, 01:25:53 am »
Maximum "nominal" supply voltage for the 4000 series is 15V. You can push it by running them at the absolute maximum ratings, but that generally isn't a very good design practice.

CD4000B series is rated for 18V supply voltage.
 

Offline GK

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #11 on: February 25, 2014, 01:39:34 am »
18V is the "absolute maximum" rating – device specifications are characterised to 15V max. You generally don’t run logic IC’s at their absolute maximum supply ratings as that gives little margin for tolerating things like switching glitches on the rails or any other possible glitch/variation.
« Last Edit: February 25, 2014, 01:45:28 am by GK »
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Offline edavid

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #12 on: February 25, 2014, 03:07:16 am »
18V is the "absolute maximum" rating – device specifications are characterised to 15V max. You generally don’t run logic IC’s at their absolute maximum supply ratings as that gives little margin for tolerating things like switching glitches on the rails or any other possible glitch/variation.

No, that is not true - 18V is allowed - see attached snippet from the CD4001B datasheet.

 

Offline GK

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #13 on: February 25, 2014, 03:29:50 am »
I didn't say it wasn't allowed -  I said 18V is the absolute maximum.

Pay particular attention to the note about "nominal" voltages in that snippet you just attached.
« Last Edit: February 25, 2014, 03:31:42 am by GK »
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Offline edavid

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #14 on: February 25, 2014, 05:51:31 am »
I didn't say it wasn't allowed -  I said 18V is the absolute maximum.

Pay particular attention to the note about "nominal" voltages in that snippet you just attached.

That is incorrect.  The datasheet states clearly that 18V is a recommended operating condition, and 20V is the absolute maximum.

« Last Edit: February 25, 2014, 05:54:50 am by edavid »
 

Offline GK

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #15 on: February 25, 2014, 06:17:01 am »
 ::)


And which manufacturer are you snipping bits of datasheet from?

The absolute maximum given by ON Semi (just one example) for the 4000 series is 18V.

If you are designing a circuit to be compatible with any 4000 series part of a specific part number, you are stuck to the lower max rated voltage.
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Offline vk6zgo

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #17 on: February 25, 2014, 10:42:10 am »
Many years ago,I used 4066's in a project,& initially left the unused switch control pins open.

The 4066's got very hot!

I returned the unused switch control pins to zero volts.

The bloody things still got hot!

Finally,I organised a minus 6.8 volt supply,& returned the switch control pins to that.

No more overheating!! ;D

Edit:-Sorry about that--hope it is less confusing now!
« Last Edit: February 25, 2014, 11:42:20 pm by vk6zgo »
 

Offline GK

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #18 on: February 25, 2014, 11:42:36 am »
So it would seem that not all 4000-series CMOS is created equal.


For compatibility reasons a nominal supply voltage of 15V max. has endured as pretty much an unofficial standard when designing with 4000 CMOS.


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Offline SeanB

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #19 on: February 25, 2014, 06:26:21 pm »
As well with analogue switches connect the unused analogue switch pins to the common ground, as these are actually inputs to the internal gates and not driven outputs. They can float and cause latch up with stray voltage fields.
 

Offline dentaku

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #20 on: February 25, 2014, 10:10:04 pm »
As well with analogue switches connect the unused analogue switch pins to the common ground, as these are actually inputs to the internal gates and not driven outputs. They can float and cause latch up with stray voltage fields.

Interesting, I didn't think that was the case.

edit... oops I forgot the word didn't in my original post :)
« Last Edit: February 26, 2014, 03:47:01 am by dentaku »
 

Offline edavid

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #21 on: February 25, 2014, 10:46:13 pm »
As well with analogue switches connect the unused analogue switch pins to the common ground, as these are actually inputs to the internal gates and not driven outputs. They can float and cause latch up with stray voltage fields.

What do you mean by this?

Look at the schematic on the TI CD4066B datasheet - the in and out terminals are not tied to any transistor gates.

http://www.ti.com/lit/ds/symlink/cd4066b.pdf
 

Offline Neganur

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #22 on: February 26, 2014, 05:26:39 pm »
you should relax a little and focus on the content of discussions :)

Where did people get the idea that it's OK to top post?  Is it a mobile thing?
 

Offline edavid

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #23 on: February 26, 2014, 06:22:30 pm »
you should relax a little and focus on the content of discussions :)

Where did people get the idea that it's OK to top post?  Is it a mobile thing?

You should stop being so relaxed and look at the format  :)
 

Offline vk6zgo

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Re: 4066 bilateral switch unused inputs and maximum voltage through switches?
« Reply #24 on: February 27, 2014, 02:26:03 am »
As well with analogue switches connect the unused analogue switch pins to the common ground, as these are actually inputs to the internal gates and not driven outputs. They can float and cause latch up with stray voltage fields.

What do you mean by this?

Look at the schematic on the TI CD4066B datasheet - the in and out terminals are not tied to any transistor gates.

http://www.ti.com/lit/ds/symlink/cd4066b.pdf

No,but no matter what the mechanism,if you leave the control pins open,the switch can draw current---& it's not always good enough to return them to common ground,see my posting above.
 


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