Using Analog Switches

[swb1]

Hi,

Has anyone switched between two circuits using an analog switch before? I have 2 serial outputs: one with .6V and another with 3.25V, where I want to allow a user to switch between the two outputs as they wish. Is there a slick way of doing this that anyone knows??

Thanks,

swb1

 

[Skogsgurra]

It depends a lot on what your signal levels are, if bipolar or positive, what current you need to source, what frequency contents the signals have, how much cross-talk you can accept and what supply voltages you have. For the task at hand, I would look at the old 4066 CMOS swicth, or a DG508 or similar. The 4066 is a very simple thing with moderatetly good channel resistance. It has four switches so you can parallel them two and two for lower switch resistance. It can be fed from TTL +5 V up to something like +18 V.

Gunnar Englund

http://www.gke.org

 

[itsmoked]

The 508 is more robust! (if I remember correctly)

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Skogsgurra]

That may be so, but it needs more exotic PSU (at least +7.5 and -7.5 V to be within specs) than the lowly 4066. The 4066 is also quite robust nowadays. No latch-up any more.

Gunnar Englund

http://www.gke.org

 

[logbook]

This request is a bit fishy. It seems you are switching digital serial lines but the logic levels are dubious.

When you say 3.25V do you mean a 0V to +3.25V logic? That is very standard.

When you say 0.6V do you mean 0V to +0.6V? That is highly non-standard. Or was it a typo?

 

[swb1]

When I say 3.25V, I mean +/- 3.25VDC with a +/- 1.25VDC threshold

When I say 0.6V, I mean +/- 0.6VDC with a +/- 0.15VDC threshold

Also the data runs at 10MHz.

Thanks,

swb1

 

[VEBill]

Any reason not to use a simple mechanical switch?

 

[Skogsgurra]

Dear swb1.

If you had told us that the signal is bipolar, you would have saved a lot of confusion. Now, you are creating even more confusion by introducing a "threshold" in the signal. A signal cannot have a threshold. What is it really that you want to do?

Gunnar Englund

http://www.gke.org

 

[nbucska]

threshold indicates that you digitize the signal using a comparator -- why not switch the digitized signal ?

Plesae read FAQ240-1032
My WEB: <

http://geocities.com/nbucska/>

 

[AllorNothing]

I have successfully used 4066 and other similar IC's to switch composite video. 1.1 V P-P. Works fine.

 

[kf6bbl]

Some of the 4000 series analog switches can work above 10MHz, some cannot.
I have sucessfully used 4051, 4052, and 4053s above 10MHz. Some 74HC40xx can go to 90-100MHz (Philips, TI, ST).
Swing range depends on your voltage rails you run it on. Use a +/-5V supply, and you can go +/-4.5V with the signals.

-Bill
CE Designer Forum

http://www.cedesigner.com

 

[swb1]

Thanks for all the input/feedback guys. One other question, anyone ever use a line driver to drive a transformer?? if so, what parts do you recommend??

Thanks,

swb1

 

[sanlog]

A fly-back schottky diode..

 

[xray]

swb1,
you might look at the maxim IC max328/329 it may be a little slow for 10 MHz but a related device may be the ticket. godd luck.

xray

 

[europus2002]

I used DG2018 , works absolutely fine and easy to control 4 switches.