analog switch IC with 8 or more SPSTs?

[choklitlove]

hi you guys.  i've been searching for something like the 4066, except with more than 4 internal switches.  i'm new to these types of ICs, so the search is difficult...  Thanks for any help!

[PRR]

Eight SPST.

That's two terminals in/out for each switch. Another terminal for control. Plus two power pins.

I count 26 pins.

DIP packages come 8 14 16 even 20 pins. And more... wasn't the 8o88 CPU in a 40-pin DIP? But the many-pin DIP packages cost a lot more. And will find fewer buyers. It is cheaper to make a million quad switch in stock 14-pin packages, and let heavy users buy two or three.

What are you really trying to do? Really 8 separate switches? Or do they come together? 8-in 1-out parts are common. 8x8 crosspoint switches exist. If you like soldering microscopic bumps there are much large crosspoint arrays.

[choklitlove]

yes, i realize it would require around that many pins.  surface mount would be fine, since it would save me from using 4 DIPs.

not positive on my desired application yet.  i have several in mind.  one is i'm attempting to sequence 8 steps of control (POTs), not voltage.  so i thought i could use the output voltages of the sequencer to trigger the switches.  8 steps, 2 POT gangs apiece, equals 16 total switches.

hopefully that made sense...  it may be stupid, I know, but I'd really like to figure it out anyway.

[Lurco]

look for "multiplexers": http://www.oup.com/us/pdf/microcircuits/students/logic/cd4051-ti.pdf

[PRR]

Now it is 16 SPST?

Minimum 50 pins.

In 4066 that is 56 pins. DIPs can be butted lengthwise so it looks like one very long DIP. The six extra power pins seem minor compared to all those signal pins.

> sequence 8 steps of control

One-of-eight? 4051 (I think {ah, Lurco confirms}). 8-in 1-out, can also be used 1-in 8-out. Put one in front of your pot-bank, one in back, wire the control pins together. Control does NOT have to share signal ground. There's just 3 control pins, which saves wires if your controller talks binary, is annoying if your control is already 1-of-8.

[~arph]

MAX335 is your friend

[R.G.]

One P-channel JFET per spst needed.

[choklitlove]

thank you guys for the responses.  i have looked at the multiplexers a lot, and i'm thinking i may not want to mess with all of the logic and serial stuff.  by that i mean the pins that depend on a certain variation of 1s and 0s to trigger the switches.  i'm just not sure i have the means or knowledge to tackle that.

however, i have gotten my need down to 8 SPSTs, so i have gotten it to work with 2 4066s.  which is fine, but i'm still open to any suggestions to get it down to one chip.  or any suggestions on how to get the previously mentioned logic to work.

thanks again though!

[choklitlove]

i posted the first circuit draft over in members only, if you'd like to check it for me!

http://www.diystompboxes.com/smfforum/index.php?topic=88673.0

[Lurco]

a counter to eight with BCD output instead of the 4017 will control the 4051 with 3 wires without diodes.

[choklitlove]

thanks for the reply.  that sounds good, any suggestions on maybe a "counter to eight with BCD output" but a little more specific?  i searched, but this stuff is really new to me so it was tough...

[JKowalski]

thanks for the reply.  that sounds good, any suggestions on maybe a "counter to eight with BCD output" but a little more specific?  i searched, but this stuff is really new to me so it was tough...

He is talking about a binary counter. It takes a clock input and posts the binary coded decimal number on its outputs.

For example, if it has 3 bits on output max:

Clock Cycle 1: 000
Clock Cycle 2: 001
Clock Cycle 3: 010
Clock Cycle 4: 011
Clock Cycle 5: 100
Clock Cycle 6: 101
Clock Cycle 7: 110
Clock Cycle 8: 111
Clock Cycle 9: usually rolls over back to 000 and starts again (only if this is the last bit in the counter, otherwise it continues counting to 1000 and etc.)

etc.

The multiplexer is usually controlled by a binary coded decimal code. This is because that if you have a 8-1 multiplexer, or 8in 1 out/ 8out 1 in, you need 8 different control code states for the eight different possible states of the multiplexer. With BCD you can represent 8 different states with three pins, as shown above.

Interfacing the above three bit counter output with the multiplexer control pins and clocking the counter connects the multiplexer in/out single pin to one of the eight in/out pins in sequence.

BCD counters usually have more than three output pins - not a problem. You can usually connect the fourth bit output to a reset which will roll over the count to zero once it hits 1000, or you can just leave it since the three lower bits will always cycle as normal even though the count gets much larger than 8.

Just look up BCD counter IC and you'll find a variety of versions.

[alparent]

Don't mean to hijack this thread but this is very interesting!
Using CMOS switching as open a lot of opportunities and is a lot of fun!

I've only played with CD4016 and CD4053 up to now.

But from my research (correct me if I'm wrong!)

Using a CD4051 controlled by a CD4518 would give me a 8 position single pole switch
and using a CD4052 controlled by a CD4520 would give me a 4 position dual pole switch.

Is that right?

Maybe there should be a "Share your switching tricks" thread stated?