non-volatile analog switch?

[Jenalee K.]

To make a non-volatile software programmable DIP switch. Anyone? Like
those non-volatile digital potentiometers.

Thanks,
Jenalee K.

 

[Luhan]

To make a non-volatile software programmable DIP switch. Anyone? Like
those non-volatile digital potentiometers.

Is this switch wired as a circuit element or is it just read by a
micro?

Luhan

 

[Joel Kolstad]

To make a non-volatile software programmable DIP switch. Anyone? Like
those non-volatile digital potentiometers.

How many DIP switches do you need? You can cheat and use those digital pots
if you don't need too many:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/238

If you're looking for something that functions as a switch for routing signals
around even when no power is available, there are some RF SPDT switches
that'll still pass a signal from one input to one output or the other with no
power applied -- they use something like a MOSFET and trap charge to keep the
channel around without power.

---Joel Kolstad

 

[Eeyore]

How many DIP switches do you need? You can cheat and use those digital pots
if you don't need too many:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/238

If you're looking for something that functions as a switch for routing signals
around even when no power is available, there are some RF SPDT switches
that'll still pass a signal from one input to one output or the other with no
power applied -- they use something like a MOSFET and trap charge to keep the
channel around without power.

How about latching relays ?

Graham

 

[Adrian Jansen]

To make a non-volatile software programmable DIP switch. Anyone? Like
those non-volatile digital potentiometers.

Thanks,
Jenalee K.

If its simply for setting options for a processor, the standard solution
is an eeprom.

If you want to actually use the paths through the switch as current
carriers to other devices, you need to implement that with a processor,
and still store the settings in the eeprom.

If there are still any parallel eproms around, you can just use one to
set the control lines of a cmos switch directly.

--
Regards,

Adrian Jansen adrianjansen at internode dot on dot net
Design Engineer J & K Micro Systems
Microcomputer solutions for industrial control
Note reply address is invalid, convert address above to machine form.

 

[Luhan]

If its simply for setting options for a processor, the standard solution
is an eeprom.

If you want to actually use the paths through the switch as current
carriers to other devices, you need to implement that with a processor,
and still store the settings in the eeprom.

If there are still any parallel eproms around, you can just use one to
set the control lines of a cmos switch directly.

Simplest solution. Microcontroller sets control lines on analog
switches, writes data to internal eeprom, goes to sleep. On powerup,
reads internal eeprom and sets control lines.

Luhan

 

[Jenalee K.]

Luhan wrote :

Is this switch wired as a circuit element or is it just read by a
micro?

Luhan

Circuit element. The idea is to not use a micro to have them set on
power on, but they must be (remotely) configurable at
installation/maintenance time by attaching a progammer. I do not want a
dedicated micro because that implicates software development and an
extra programming operation at production time. I do not want real DIP
switches because users tend to change their settings and today
everything has to be software configurable anyway.

Thanks,
Jenalee K.

 

[Jenalee K.]

Eeyore wrote :

How about latching relays ?

Graham

Latching relays (price?) could work but I'd have to add circuitry to
read back the actual position.

Thanks,
Jenalee K.

 

[Jenalee K.]

Joel Kolstad wrote :

How many DIP switches do you need? You can cheat and use those digital pots
if you don't need too many:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/238

If you're looking for something that functions as a switch for routing signals
around even when no power is available, there are some RF SPDT switches
that'll still pass a signal from one input to one output or the other with no
power applied -- they use something like a MOSFET and trap charge to keep the
channel around without power.

---Joel Kolstad

Great info, Joel. I'd thought about using digital pots but their off
resistance would be too low (up to 200k). And their bandwidth is a bit
limited. This appnote is a better way.

Do you have any references for those RF SPDT switches?

Thanks,
Jenalee K.

 

[Joel Kolstad]

Hi Jenalee,

Do you have any references for those RF SPDT switches?

Hmm... I thought I did, but now I'm thinking I was mistaken in how the switch
actually work. I believe what I looked at was
http://www.peregrine-semi.com/pdf/datasheets/pe42742ds.pdf, but looking at it
more closely it always assumes one state when power is removed, so it wouldn't
work in your application. Sorry for the confusion.

---Joel