Square Wave Generator Based on 555 Question.

[PCB.Wiz]

I found an interesting version which goes up to 2.5 megahertz.  In their datasheet it talks about exactly that, being able to run a stable mode with one resistor.
http://www.aldinc.com/pdf/ALD7555-7556.pdf

That part is not cheap, but it does have impressive PSRR on the graphs. (tho not reflected in the tables ? )

And for a bit of a twist in 555 variants, here's one built with a (non-volatile) programable decade counter:

https://www.customsiliconsolutions.com/downloads/Revised%20Standard%20products/CSS555_Spec_2.pdf

(see page 2 for a block diagram)

Coming from a 12C509 programming history, after all these years I'm still not exactly sure which niche the CSS555 fulfils.

Yes, the CSS555 is also not cheap. However, it does manage good precision with small caps and low uA. (typ 1% and 35 ppm/°C )

MCU's alone struggle to match the Icc/precision levels, as most low power oscillators in MCU focus on power first, and dF/dT and dF/dV later.
Many fail to even spec tempco and PSRR of their low power osc.

The emergence of 20c MCUs has pushed the low power 555 into smaller niches.
A MCU with a 32kHz crystal can still cost less than a CSS555, and the crystal leapfrogs into much better precision.
Some MCUs allow you to calibrate the poor kHz osc against the better MHz osc, at some small code and icc cost.
 

[JJ_023]

And for a bit of a twist in 555 variants, here's one built with a (non-volatile) programable decade counter:

https://www.customsiliconsolutions.com/downloads/Revised%20Standard%20products/CSS555_Spec_2.pdf

(see page 2 for a block diagram)

Coming from a 12C509 programming history, after all these years I'm still not exactly sure which niche the CSS555 fulfils.

Thank you for sharing that.  I read the datasheet. The only niche that I could possibly see is in applications where you might need to modify the  frequency by programming the onboard EEPROM.   The other niche is that they claim to require the least amount of power, so maybe in certain battery longevity applications it would make sense as well.

It's also rather expensive at almost $3.

At 1/3 of the price you could get the Texas Instrument version (LMC555 CMOS Timer). Which in my opinion is superior in almost every manner.

https://www.ti.com/lit/ds/symlink/lmc555.pdf

[JJ_023]

I found an interesting version which goes up to 2.5 megahertz.  In their datasheet it talks about exactly that, being able to run a stable mode with one resistor.
http://www.aldinc.com/pdf/ALD7555-7556.pdf

That part is not cheap, but it does have impressive PSRR on the graphs. (tho not reflected in the tables ? )

And for a bit of a twist in 555 variants, here's one built with a (non-volatile) programable decade counter:

https://www.customsiliconsolutions.com/downloads/Revised%20Standard%20products/CSS555_Spec_2.pdf

(see page 2 for a block diagram)

Coming from a 12C509 programming history, after all these years I'm still not exactly sure which niche the CSS555 fulfils.

Yes, the CSS555 is also not cheap. However, it does manage good precision with small caps and low uA. (typ 1% and 35 ppm/°C )

MCU's alone struggle to match the Icc/precision levels, as most low power oscillators in MCU focus on power first, and dF/dT and dF/dV later.
Many fail to even spec tempco and PSRR of their low power osc.

The emergence of 20c MCUs has pushed the low power 555 into smaller niches.
A MCU with a 32kHz crystal can still cost less than a CSS555, and the crystal leapfrogs into much better precision.
Some MCUs allow you to calibrate the poor kHz osc against the better MHz osc, at some small code and icc cost.

Thank you for your opinion.  What do you think of the Texas Instrument version (LMC555 CMOS Timer)?

https://www.ti.com/lit/ds/symlink/lmc555.pdf

[PCB.Wiz]

  What do you think of the Texas Instrument version (LMC555 CMOS Timer)?
https://www.ti.com/lit/ds/symlink/lmc555.pdf

That's a different point on the price/performance curve.
LMC555 specs typ 100uA at 5V and 75 ppm/°C, so that's a distant second to CSS555 specs of 4.3µA at 5V and 35 ppm/°C.

Of course, you need to decide how much you are prepared to pay for the better numbers 

For other price curve info, look at lcsc which has CMOS 555 for sub 8c/500 - any of those could be 'good enough' for most use cases.

[JJ_023]

  What do you think of the Texas Instrument version (LMC555 CMOS Timer)?
https://www.ti.com/lit/ds/symlink/lmc555.pdf

That's a different point on the price/performance curve.
LMC555 specs typ 100uA at 5V and 75 ppm/°C, so that's a distant second to CSS555 specs of 4.3µA at 5V and 35 ppm/°C.

Of course, you need to decide how much you are prepared to pay for the better numbers 

For other price curve info, look at lcsc which has CMOS 555 for sub 8c/500 - any of those could be 'good enough' for most use cases.

How do those 2 compare at 12V? 

All kidding aside I do appreciate the different variations.  If I needed whatever specs I would definitely be willing to pay for it.  The reason I chose SE555 was they were fairly cheap when I got them and most importantly they have a higher voltage tolerance than most variants.  Often times I use them in Monostable to debounce switches for a variety of applications.  It's a really cheap way to get a crisp button press.

I know they have specific purpose built chips for debounce, and they definitely work but they are sometimes a little too expensive in the grand scheme of things.

Again thanks for all the additional info.

[zapta]

One way to achieve 50% with a 555 is to use it as a Schmidt trigger. Something along this diagram.

[RoGeorge]

- a very short spike right after each signal edge - that is from the inductance of the GND alligator wire.

You say the spike is at the end of the waveform I thought that was the beginning of the waveform.

The ringing spike is expected to appear after each edge in that signal (I didn't say at the end of the waveform).  An edge can be either falling-edge or raising-edge.

The forum is in maintenance, works intermittently, and the old forum bug about attachements seems to be back again etc., plus that this thread is moving too fast, and in many directions at the same time.  I'm afraid I won't be able to keep my promise of going into details about the requested pics.  Thank you for attaching them.  The currently attached waveforms are much better than the ones in the OP.

Looks good, keep experimenting! 

[JJ_023]

One way to achieve 50% with a 555 is to use it as a Schmidt trigger. Something along this diagram.

Thank you for taking the time for the schematic.  I believe I already did this based on someone else's suggestion with the results posted in reply number 45.  I wasn't able to achieve a 50% duty cycle.  It was explained to me that is most likely because my 555 variant is not a CMOS variant. 

In post number 4 you can see the schematic used.  I use that particular schematic omitting the 100 K resistor.  Unless I am mistaken the circuit is basically what you are suggesting.

[JJ_023]

- a very short spike right after each signal edge - that is from the inductance of the GND alligator wire.

You say the spike is at the end of the waveform I thought that was the beginning of the waveform.

The ringing spike is expected to appear after each edge in that signal (I didn't say at the end of the waveform).  An edge can be either falling-edge or raising-edge.

The forum is in maintenance, works intermittently, and the old forum bug about attachements seems to be back again etc., plus that this thread is moving too fast, and in many directions at the same time.  I'm afraid I won't be able to keep my promise of going into details about the requested pics.  Thank you for attaching them.  The currently attached waveforms are much better than the ones in the OP.

Looks good, keep experimenting! 

Thank you for clarifying the ringing.  That was an oversight on my part.  When I was writing that post there were issues with the site being down.  No worries about your promise I totally understand.  Thanks to your contributions.