Author Topic: Waveforms in a 74LS04 ring oscillator.  (Read 28078 times)

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Offline joeqsmith

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #75 on: April 09, 2015, 10:09:44 pm »
Looks like you are off to a good start.   Check the pg 8 of the data sheet you provided the link to for the termination.  VTT=VCC-2.0.  I would use that last gates to drive the DSO.      I checked and only have the real old 80s Motorola book that covers the 10K and earlier.   Does not seem like you would want the series terminator but could be wrong.
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Offline JoeN

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #76 on: April 09, 2015, 11:10:12 pm »
Looks like you are off to a good start.   Check the pg 8 of the data sheet you provided the link to for the termination.  VTT=VCC-2.0.  I would use that last gates to drive the DSO.      I checked and only have the real old 80s Motorola book that covers the 10K and earlier.   Does not seem like you would want the series terminator but could be wrong.

So, on closer inspection, you recommend terminating it this way:



So it recommends terminating to Vtt instead of Vee, right?  Vtt would be 3.0V in this case.  Should I throw on a regulator to create that voltage?

And why no series termination?  I see 50 ohm resistors in series on this schematic so that is why I put them on my schematic.  I could leave the 0805 footprint in there and drop in a 0 ohm resistor and see if it matters.  Does that sounds OK or would a 0 ohm resistor affect the circuit?  I'm going to get 3 boards in any case and I have five of these ICs total.

Micrel seems to recommend terminating to Vee which is why I did that at first:  http://www.micrel.com/_PDF/HBW/App-Notes/termination.pdf

By using the last gate to "drive the DSO" are you meaning the RF output and assuming an oscilloscope on the output?  What advantage does this give, will having a buffer square up the output a bit since it is no longer also driving a gate?
« Last Edit: April 09, 2015, 11:23:13 pm by JoeN »
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Offline T3sl4co1l

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #77 on: April 10, 2015, 02:29:52 am »
No, those aren't series terminations, those are indicating to use 50 ohm transmission lines. :)

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Offline joeqsmith

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #78 on: April 10, 2015, 02:32:05 am »
I am only suggesting to check the data sheet.   Micrel app note you link to, see figures 3&4.    Take the time to read it.   

Zo is not a resistor. 

Adding any discontinuity, like a zero ohm jump will cause some reflection.   Higher speeds, need to pay more attention.

You could make a few different boards on the one panel to try different ideas out.   

Quote
By using the last gate to "drive the DSO" are you meaning the RF output and assuming an oscilloscope on the output?  What advantage does this give, will having a buffer square up the output a bit since it is no longer also driving a gate?

Yes.  Isolation.   

I have not used ECL in many years.   You should have no problem getting something to work on a circuit board.   This is a very short video I put together showing a single PECL FF on an a VERY crude X-acto knife board.  The videos not real exciting  but does show you can clock some of them well into the GHz range as mentioned.   

https://www.youtube.com/watch?v=k1pUlJwJzAI&feature=youtu.be

Looking forward to seeing what you get working.
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Offline JoeN

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #79 on: April 10, 2015, 02:36:03 am »
I am only suggesting to check the data sheet.   Micrel app note you link to, see figures 3&4.    Take the time to read it.   

Zo is not a resistor. 

Adding any discontinuity, like a zero ohm jump will cause some reflection.   Higher speeds, need to pay more attention.

You could make a few different boards on the one panel to try different ideas out.   

Quote
By using the last gate to "drive the DSO" are you meaning the RF output and assuming an oscilloscope on the output?  What advantage does this give, will having a buffer square up the output a bit since it is no longer also driving a gate?

Yes.  Isolation.   

I have not used ECL in many years.   You should have no problem getting something to work on a circuit board.   This is a very short video I put together showing a single PECL FF on an a VERY crude X-acto knife board.  The videos not real exciting  but does show you can clock some of them well into the GHz range as mentioned.   

https://www.youtube.com/watch?v=k1pUlJwJzAI&feature=youtu.be

Looking forward to seeing what you get working.

Thanks for the info.  If you say those series resistors are definitely not necessary then they come off, no problem.  Probably save a few cents on the board and keep the traces a bit shorter.  My idea of a regulator to supply 3.0V for the 50 ohm parallel terminator resistors, is that a good idea?  If so, maybe I can get this design out tomorrow to OSH and then we have to wait a couple of weeks.  Thanks for your help.
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Offline joeqsmith

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #80 on: April 10, 2015, 03:11:25 am »
From your Micrel note:

Quote
"As a result of ECL/PECL’s differential, high input impedance, very low output impedance (Open Emitter), and small signal swing (andresulting low EMI), ECL/PECL is ideal for driving 50? and 100? controlled impedance transmission lines. A signal trace is considered a transmission line, thus requiring termination, when the signal’s rise/fall time is faster than a trace’s round-trip propagation delay. In some applications, if the distance between two devices is short enough, then termination may not be necessary. Another way to express this is: If, T RISE(signal) < 2 × TPD(trace), then the trace is a transmission line and proper termination is required"

I am not sure how the Micrel note applies to the parts you are playing with.


Quote
My idea of a regulator to supply 3.0V for the 50 ohm parallel terminator resistors, is that a good idea?

Personally, I would just use what is shown in Fig 3 or 4 and forget using another supply.   Doubt you really care about the added power.       Really if you want to play with it, I would recommend you try all three.  Then one without termination and one with series termination just to see what the effects are.     Seems like all 5 circuits should fit on a small board.   
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Offline GK

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #81 on: April 10, 2015, 10:18:05 am »
Potato semi's so called GHz logic might be interesting to play with/try. Parts can be had from their on-line store in small qty.

http://www.potatosemi.com/
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Offline dannyf

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #82 on: April 10, 2015, 11:29:10 am »
74HC132 -> 120Mhz for single gate and 40Mhz+ for 3 gates, all at 5v. 3 gates work down to 2Mhz @ 1v and 60Mhz+ at 10v (yes, 10v).
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Offline JoeN

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #83 on: April 10, 2015, 08:38:27 pm »
Potato semi's so called GHz logic might be interesting to play with/try. Parts can be had from their on-line store in small qty.

http://www.potatosemi.com/

I am sort of surprised I haven't heard of them and never got a hit on them on eBay during other searches.  Sort of interesting.  I do think they need a new logo and name though, the current choices are pretty lame.  I know it doesn't matter as far as their product goes, but really it does actually matter at some point to generate enough confidence that the company is a serious entity that will be there in a few years.  I wonder if they have any serious customers.
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Offline tggzzz

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #84 on: April 10, 2015, 09:02:11 pm »
Potato semi's so called GHz logic might be interesting to play with/try. Parts can be had from their on-line store in small qty.

http://www.potatosemi.com/

I am sort of surprised I haven't heard of them and never got a hit on them on eBay during other searches.  Sort of interesting.  I do think they need a new logo and name though, the current choices are pretty lame.  I know it doesn't matter as far as their product goes, but really it does actually matter at some point to generate enough confidence that the company is a serious entity that will be there in a few years.  I wonder if they have any serious customers.

Good question. Personally I am put off by them still having the Vcc/GND pins as far away from each other as they can. I disliked that in the late 70s, and haven't seen any reason tochange my mind.
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Offline joeqsmith

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #85 on: April 10, 2015, 11:51:50 pm »
I thought it was an April fools website complete with data sheets for potato chips.    :-DD :-DD :-DD :-DD
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Offline dannyf

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #86 on: April 11, 2015, 12:09:13 am »
For hobby uses, it seems to be OK - whenever ebay parts are OK, those potato chips should be ok too.

Anything above that, I would think twice about using them.
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Offline joeqsmith

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #87 on: April 11, 2015, 01:11:10 pm »
74HC132 -> 120Mhz for single gate and 40Mhz+ for 3 gates, all at 5v. 3 gates work down to 2Mhz @ 1v and 60Mhz+ at 10v (yes, 10v).


1/2*120M*1 = 4.2nS = 1/2*40M*3.  Yea, the math works.  :-DD    Sounds like your numbers are on par with mine.   I am a bit surprised it would run at 10 volts.  What is the exact part you used?   I have a few duplicate parts I could run up to failure and see what I get. 

The OP had started out with 5 gates, then dropped it to 3.   I am not sure why but guess they wanted it running slow enough that they could make the measurement with the equipment they have available.   

With JoeN trying ECL, we could see some faster numbers.  It will be interesting to see what they get working. 
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Offline dannyf

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #88 on: April 11, 2015, 08:15:39 pm »
The HC132 I used earlier was actually an AHC132 (SN74AHC132 by TI).

I drop'd in a HC00 (Philips) and got similar results (95Mhz vs. 120Mhz, one gate only).
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Offline dannyf

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #89 on: April 12, 2015, 12:29:49 am »
Tried some MM74HC00 from ST. 75Mhz tops (1 gate, 10v).

This thing can be made into local oscillators. With a mixer + LPF, you get a direct conversion, pot-turned radio.
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Offline joeqsmith

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #90 on: April 12, 2015, 03:16:29 am »
Tried some MM74HC00 from ST. 75Mhz tops (1 gate, 10v).

This thing can be made into local oscillators. With a mixer + LPF, you get a direct conversion, pot-turned radio.

This would make IMO an interesting thread.    :-+ 
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Offline dannyf

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #91 on: April 12, 2015, 01:20:05 pm »
current consumption for the MM74HC00 part:

12ma @ 5v;
56ma @ 12v (yes, 12v)
250ma @ 20v (yes, 20v, for a 5v part).
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Online Zero999

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #92 on: April 12, 2015, 04:42:11 pm »
At what voltage does it release magic smoke?
 

Offline joeqsmith

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #93 on: April 12, 2015, 05:34:01 pm »
 :scared: :scared:

When you measure the current, are you using all four gates?    Curious how much is the loading and how much is the part. 

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Offline dannyf

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #94 on: April 12, 2015, 06:33:46 pm »
All four gates were used.
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Offline joeqsmith

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #95 on: April 14, 2015, 01:47:30 am »
I set the jig to sweep from 2.6 to 24 volts, with the current limit set to 6 amps.   It did not provide me with the excitement  I had hoped for.   The counter's input impedance was set to 1Meg rather than 50 ohms to limit the load current and prevent damage to the front end.  Nothing else was changed in the test setup. 

Looking at the 4069, you can see how the frequency actually starts to fold back.  This is very reproducible.   This is the only part the survived. 

The 74HC04 didn't just fail.  It sort of slowly died after 11.2 volts.

The 74AC14 died real quick after 8.4 volts.   You can see it trying to stay alive for a few more cycles..   

Damage2 is zoomed into the area where the HC and AC devices failed.


No smoke, no plastic fragments.....
« Last Edit: April 14, 2015, 11:51:30 pm by joeqsmith »
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Offline joeqsmith

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #96 on: April 14, 2015, 11:59:59 pm »
Found an duplicate Harris HC part which ran all the way out to 15.2 volts.  Notice again how the frequency was falling off just prior to failure.   Again, no real excitement. 

Grabbed an old Fairchild TTL part thinking that would certainly actually blow up...  It did!   

What's real interesting is how the TTL parts frequency fell way off, then it takes such a radical jump, rolls off again, then dies a flaming smoke filled room kinda death.

If you found an HC part that runs to 20 volts as you suggest and is linear, stick with that part.   


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Offline joeqsmith

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #97 on: September 23, 2016, 06:00:34 pm »
An old National 54F04 military device.  Not as fast as the Fairchild F04.   Also ran it up to 110 and down to -12C. 
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Offline David Hess

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Re: Waveforms in a 74LS04 ring oscillator.
« Reply #98 on: September 23, 2016, 08:55:28 pm »
In the past when building these types of test circuits, I usually included a fast discrete JFET or bipolar buffer to drive a 50 ohm transmission line directly to the oscilloscope.  I guess now there are some integrated buffers or operational amplifiers which could do the same thing.
 


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