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Is the 555 still a viable IC?

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ejeffrey:

--- Quote from: baldurn on February 18, 2024, 02:39:56 am ---Funny that you say software development is the reason to avoid a MCU and use 555. These days most people think the other way around. We go with a MCU even when a 555 would have done the job. It is easier to figure out a simple program than it is to do "real" EE with discrete components.

--- End quote ---

I don't think programming an MCU is any more or less "real" than configuring a 555.  I don't think trying to make a value judgement there is helpful.  But there is a big difference in what makes sense for a hobby project, prototype, or one-off than for something that is going to need to be manufactured and supported in production.

An MCU is great because it's super flexible, you can drop it in your schematic and start manufacturing without even being sure what you need it to do. It also can easily be hooked up to a computer for automation.  But in a manufacturing setting, even for low volume it adds steps to the process and additional configuration to manage.  Unless you as the designer wants to manually program hundreds or thousands of units before they go to end users you need to document the flash process and make sure your manufacturer is doing it correctly, and possibly deal with a situation where the process was messed up and you have a bunch of defective units in inventory that need reflashing.  You can order pre programmed chips for a reasonable setup cost and that's a decent option but still comes with process overhead.

Again, in high volume you can sort this out and it's worth it to save a few cents on the BOM.  Or more likely you integrate the functionality into a part that already exists on the design and ask the software team to add some timers to their existing code base.  But for low volume products I have found that the fewer programmable devices  the better.

Zero999:
Another example of a digial replacement is the 74HC5555, but it's no longer made.
https://www.mouser.com/datasheet/2/302/74HC5555-1597181.pdf

The original NE555 is not the most beginner friendly of ICs. It draws nasty spikes, when the output changes state, which can cause interference and spurious triggering.

Newer CMOS variants such as the TLC555 and ICM7555 don't have the same issue of current spikes, but they have much weaker output pins, especially when sourcing.

ejeffrey:
Also to be clear , I'm not suggesting nobody should use a MCU when a 555 will do the job.  Just that there are factors beyond per unit cost, and that the programmability of a MCU is not always in the + column.  As always it is situational but I don't think the 555 is obsolete even when a small microcontroller can do many (but not all) of the same jobs for lower cost.

Bud:
I am wondering why noone yet said "Just use an FPGA!", as it typically happens.  :palm:

Ian.M:
Hmm.  FPGA board with three ADCs, and some level shifters and output drivers implementing a soft core CPU running a SPICE simulation of  a 555 in realtime . . .  :-+  :popcorn:  :wtf:

The only flies in the ointment are the quiescent current, power dissipation and board area used!  :--  :palm:  Lets not even mention the price.  |O

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