Multiplex 1 output to 12

[LMorr.3]

Hello,

What is the best way to multiplex an output pin to 12 output signals?  I currently have 1 output sourcing 3.3v through a 1k resistor which works well, but need it multiplexed to 12 identical outputs.  I see the STM32F373 has a max rating of 15mA for output pins so looking for advice on the best way to handle this.

Many thanks,

[Andrew Neil]

I think we need more details of the nature of this output signal, what it has to feed, and what you mean by "multiplexing" here, and what are the constraints, timing requirements, etc ?

A diagram might help ...

[LMorr.3]

Here is more detail:  The main uC can connect up to 12 other uCs.  The main uC can send a 3.3V signal 'trigger' signal to other uCs via an output pin.  Currently, I have the main uC sending successfully to 1 other uC but now need to duplicate ( multiplex ) the signal to all other uCs.  Looking at using TI parts but will need 2 and may be overkill.  

Many thanks,

[SofLit]

Need to be more specific.

What do you mean by "an output pin"? Analog output ex: from F3 DAC? 

[SofLit]

https://www.nexperia.com/products/analog-logic-ics/analog-switches-and-multiplexers/analog-switches/74HC4067PW.html

[Andrew Neil]

Still too vague.

The F373 is available with up to 100 pins - could you not just use 1 pin per "signal" ?

I2C ?

[Danish1]

Where did you see this rating of 15uA (microamps)?

I would expect the rating to be 15mA (milliamps), 1000 times as much.

I think you are misunderstanding the term Multiplex. That is where different signals are shared on the same pin. Perhaps a better term for what I understand you want is fan-out. And where you are driving only CMOS inputs the fan-out is unlimited (subject to speed issues caused by stray capacitance). And this can be improved by Buffering

You might want to consider ESD protection where signals go from one pcb to another, or opto-isolation if they might not share the same Vss.

[Andrew Neil]

@LMorr.3  It's still unclear what your requirement here is.

As @Danish1 suggests, it's not even clear what you mean by the term "multiplex"

Again, a diagram may help.

[LMorr.3]

You are correct, I meant mA and not uA.  Fan-out is also good term to describe what I was looking for.  Good to know the fan-out for CMOS is unlimited.  I also have another case where I"m planning on using multiple SN74AHCT1G125 parts and will drive them with 1 output pin.  

[LCE]

Check the load again, when driving 12 GPIOs = hi Z inputs of other MCUs, the STM32 output driver should be good enough.

And what Andrew said, what about using more pins?
You could use a complete GPIO-bank to drive the pins in sync.