[sdiy] Best way to limit current through an analog switch IC?

[Pete Hartman]

I once had a project where I wanted to use the small pcb mounted relays,
and I found that  the ones I found weren't rated for extended on times --
they were basically meant for momentary use only, which didn't suit the
application.

I'm sure there are probably ones (at a higher price point than I was
willing to go to) that don't have that limitation, but definitely review
your data sheets carefully for that characteristic.

I ended up using a combination of a 4pdt switch and vn104 fets which have
very low R-on.  Was trying to replace a massive 9 pole switch for a euro
layout.  It worked well enough but I wasn't entirely happy with it so it's
in the pile of shame...

Pete




On Wed, Jul 3, 2024 at 12:08 AM Roman via Synth-diy <synth-diy at synth-diy.org>
wrote:

> You could always use relays intead of a mux.
>
> CV friendly and pretty high current capacity.
>
> Roman
>
>
> ---- Użytkownik Paul Glass-Steel via Synth-diy napisał ----
>
> The switching function is ancillary to the module's primary function as a
> window comparator; if I have to choose between bidirectional or pitch-CV
> friendly, I'll take bidirectional. But, if I can have both at the cost of
> some complexity - it's middling-complex already, so what's a bit more,
> perhaps?
>
> On Tue, Jul 2, 2024 at 2:52 PM Mattias Rickardsson <mr at analogue.org>
> wrote:
>
>> Does it have to be bidirectional?
>> Feels like this is the trickiest part to get around. :-)
>>
>> /mr
>>
>>
>> Den tis 2 juli 2024 17:08Paul Glass-Steel via Synth-diy <
>> synth-diy at synth-diy.org> skrev:
>>
>>> Hello all,
>>>
>>> I'm working up a bi-directional switch module around the TI MUX507
>>> analog switch IC. The datasheet lists the maximum IO current as 30mA. I'd
>>> like to proof the switch against the fault condition of having the IO
>>> spanning my +/- 12V rails, however remote that mis-connection might be.
>>>
>>> By Ohm's law, the bulk series resistor needed would be 820R 1W, rounding
>>> to common values. I imagine that resistance would be high enough to audibly
>>> affect pitch CV. Is there a better or more elegant solution to limit the
>>> current?
>>>
>>> Thanks,
>>> -Paul
>>>
>>>
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