micro power square wave oscillator

[Jonathan Kirwan]

<snip>
First, low voltage. A fresh silver cell is just 1.55V. Then the clock
never really feeds anything except the input of a divider chain within
the chip. They'll probably do their darndest to keep its capacitance to
a minimum.

It does seem clear that's important.

A square wave oscillator won't be a nice resonant architecture. So
you'll have to muscle capacitive charges around and it will consume more
power. It's like wanting to rapidly move the pendulum of a grandfather's
clock between its end points. This is why the OP might want to think
about whether it really has to be a square wave.

That was helpful. Do you imagine that they may use an LC, though, and
attemp to retain as much energy there as possible? Or, as you seem to
suggest to me, graduate the transfer of charge more trapezoidally and
not use magnetic field storage, at all?

I kind of imagine that the usual crystal model most of us are likely
to use has also been tremendously refined by watchmakers into a very,
very proprietary one -- one that models the physics much better -- and
that they use that in combination with thoughtful design. But I have
to say that everytime I think about trying to do a 32kHz oscillator at
very low power using discrete parts I just learn to appreciate how
much good work has gone into what is now a very cheap watch.

Jon

 

[[email protected]]

39:23 -0700 (PDT), [email protected] wrote:
On Jul 2, 9:40 am, [email protected] wrote:

<snip>

Post it yourself, if you are so keen to see it. The OP hasn't asked
for it, and I'm not motivated to do you any favours.

---
Is English not your first language?

Here's the OP's post, ya goddam liar:

"I'm looking for a schematic for a square wave oscillator which draws
around 10uA, powered by 2 to 5V and oscillates at around 100kHz with a
50% duty cycle. I tried out some schematics around a 4007 but none can
meet all the requirements.

any suggestions here?

He's had enough feedback to let him get on and do something for
himself if he's anything like competent - and this is
sci.electroncs.design, not sci.electronics.basics. If he really wants
a schematic he could e-mail me directly (the e-mail address I post
here is real and has been since before people strarted harvesting
them) or he could ask here. Without that much feedback, I'm not going
to bother.

You failed your chance to prove your own competence. An emitter-
coupled monstable can't be made to produce a 50% duty cycle, and if
you operated at my level, you'd know - or be able to work it out.

You did, and now you're trying desperately to get off the hook using
any lame excuse you can lay your hands on, LOL!

So you'd like to think. Dream on.

 

[whit3rd]

I'm looking for a schematic for a square wave oscillator which draws
around 10uA, powered by 2 to 5V and oscillates at around 100kHz with a
50% duty cycle.

Well, a 74HC14 will work at that power input and
it oscillates fine with a single resistor and capacitor
(remember to ground the five unused inputs).

Alas, the quiescent current with that one input floating
around the threshold is not as low as one would like.
An old RCA application note, ICAN-6230, seems to indicate
that 100 kHz operation will be well over a milliwatt (at
5V, that means 200 uA). That note was on the old 4000
series CMOS, though, so you might find the 'HC series
can outperform that analysis.

Others have suggested discrete transistor oscillators; that's
your best bet. An LC or mechanical resonator (OK, quartz
crystal or ceramic nowadays, but I still recall tuning forks
with coils of wire...) can be less lossy than an RC timer.

 

[[email protected]]

You failed your chance to prove your own competence. An emitter-
coupled monstable can't be made to produce a 50% duty cycle, and if
you operated at my level, you'd know - or be able to work it out.

[snip]

As usual Slowman is so full of shit his eyes are brown, see my 50%
duty cycle device from the mid-60's...

http://analog-innovations.com/SED/MC1658-DataSheet.pdf

For once Jim has got a detail right - my eyes are brown - but (as
usual) the rest of the message is severely out of touch with reality.
Given as many transistors to play with as Jim used in the MC1658 even
I could probably make a sort of emitter-coupled multivibrator with a
50% duty cycle (though it would certainly involve a lot of false
starts). The classic two-transistor emitter-coupled multivibrator is
rather less flexible. The OP application would probably require a
third transistor to get enough voltage swing at the output.

 

[Joerg]

They also current limit the drive to the crystal. PIC datasheets have a
warning in the small print to use a series resistor when using watch
crystals in low power mode to avoid overdriving them. I have seen the
odd PIC manage 12uA running on a 3v supply with a 32768Hz xtal (ISTR the
CPUs square wave clock is then 8192Hz) which isn't too far off the spec.

100kHz would obviously be a bit more thirsty for juice.

Loose use of words? I assumed he wanted a good squarewave buffered
output, but probably does not care about the internals.

Sure, that's why I suggested to try a very low power VCC monitoring chip
as oscillator. Whether it'll get low enough in Ic I don't kniow, haven't
tried yet.

The crystal is gently driven and the sine waveform amplified by a buffer
to generate the square wave clock. An xtal has very high Q so it doesn't
need much encouragement apart from initially to start up.

Yes, but one has to watch out for capacitances in the last stage, the
one to square up the waveform. Every pF counts.

I suspect it would be OK using a watch xtal 32kHz or 100kHz. Although I
have never tried to do it with discrete parts.

He might need a custom made 100kHz crystal or try something on the 3rd
of a watch crystal but that won't be exactly 100kHz.

 

[[email protected]]

Which is all you can produce on the subject.

And how are you planning to meet the 10µA spec?

By using a couple of low capacitance parts - as you'd be aware if
you'd read and understood what has already been posted in this thread.

Got a schematic?

Persistent whining may have worked on your mother but it won't do you
any good here.

 

[Fred Bartoli]

Jim Thompson a écrit :

That drives U1A's input diodes...naughty naughty!

[snip]

On-chip, which is where I do that, there are NO ESD diodes ;-)

And I use single stage inverters ala 'HCU04 except much smaller.

Delete R4/R5 and replace the cap with a two identical caps divider.
(and you're saving one component)

 

[[email protected]]

---
He already did ask here, so why don't you just post what you've got?

LOL, as if you had anything to post except excuses...
---

As if I had anything to post that you could understand - you may be
able to pose as a guru on sci.electronics.basis, but around here you
are a rube.

---
What a crock of shit.

The fact is that you don't have a schematic, or a clue, and _can't_
post anything which even remotely meets the OP's requirements.

If you had mastered more than minimal literacy, you'd realise that I
never claimed that an emitter-coupled monstable could be persuaded to
produce a 50% duty cycle - I merely invited you to attempt the
impossible (in the context of a two-transistor circuit, which Jim's
MC1658 isn't). A slightly more perceptive reader would have got the
message from way I worded the invitation, even if they were as
ignorant about multivibrators as you have proved to be.

This isn't the first time you've failed to read what I've actually
written and I was fairly sure that I could give you enough rope to
hang yourself.

I've known that for a long time and that's why I don't usually waste
my time bothering with checking your posts for accuracy, since
bringing the errors to your attention just results in your usual song
and dance attempt at avoiding the issue.
---

You do make these claims. Who do you think is going to believe them?

You've made a fool of yourself and are now retreating behind the usual
screen of scatalogical abuse.

 

[[email protected]]

Your spell-checker is right, for what that's worth. The dictionary
spelling is "scatological" and Google throws up 311,000 examples of
that versus 56,700 for "scatalogical". Since the vowel in question is
unstressed and thus pronounced with a schwa, even you wouldn't bother
to get excited about it if you weren't a loser scrabbling to save
face,

It is a tolerably low frequency word - thirteen in every 100 millions
words of English, which puts it at position 97,576 down the word
frequency table. Kucera-Francis doesn't even list it

 

[[email protected]]

On Jul 3, 11:39 am, Jim Thompson <To-Email-Use-The-Envelope-I...@My-
Web-Site.com> wrote:
On Wed, 2 Jul 2008 17:55:22 -0700 (PDT), [email protected] wrote:
[snip]
If you wanted to prove how clever you are. you could try to post a
circuit for a 50% duty cycle emitter-coupled astable multvibrator-
the smaller voltage swing at the active devices would reduce the
current consumption over the more familiar collector-coupled design,
and would make it easier to preserve a thin base-emtter junction,if
you could get it to work.
---
Since I'm not the one who made any wild-ass bullshit claims I don't
have to prove anything.
You failed your chance to prove your own competence. An emitter-
coupled monstable can't be made to produce a 50% duty cycle, and if
you operated at my level, you'd know - or be able to work it out.
[snip]
As usual Slowman is so full of shit his eyes are brown, see my 50%
duty cycle device from the mid-60's...
http://analog-innovations.com/SED/MC1658-DataSheet.pdf
For once Jim has got a detail right - my eyes are brown - but (as
usual) the rest of the message is severely out of touch with reality.

He states that you're full of shit and that's certainly real enough.
---

And how are you planning to meet the 10µA spec?

Got a schematic?

JF

http://analog-innovations.com/SED/EmitterCoupledOscillator.pdf

Not exactly a realistic circuit. Where is the OP going to get 500k
resistors? It isn't an E12 value, or even E24.

And a 0,265V voltage swing isn't all that useful. The classic two-
transistor emitter-coupled multivibrator has a free collector output,
usually used to drive a third - complementary - transistor as a
saturating switch to provide a rail-to-rail output.

And why use the 2N3904? The BFR92 has much lower internal capacitance
(and a much higher bandwidth) and could probably run with less than a
microamp in either leg. The BFT92 could serve as the saturating
switch.

You could presumably get a decent voltage swing out of Jim's circuit
by adding three more transistors - a long-tailed pair driven from one
of the emitters, and a satuarating switch driven from one of the free
collectors. The tail wouldn't be all that long - only a quarter of a
volt - and you might tap the emitter resistor to trade off voltage
swing for extra DC bias.

With the BFR92 and the BFT92 you could perhaps drive all five
transistors within your 4uA current budget - the OP asked for a supply
voltage range of 2V to 5V and with this approach 10uA at 5V only
leaves you with 4uA at 2V.

Neither of the data sheets I've cited for the BFR92 and BFT92 says
anything about the forward base-emitter voltage drop so you would be
designing around an unspecified parameter.

 

[Joerg]

On Jul 4, 3:03 am, Jim Thompson <To-Email-Use-The-Envelope-I...@My-Web-
Site.com> wrote:
[...]

http://analog-innovations.com/SED/EmitterCoupledOscillator.pdf

Not exactly a realistic circuit. Where is the OP going to get 500k
resistors? It isn't an E12 value, or even E24.

C'mon, that's just an entry from the sims. Use 470K, 499K, whatever.

And a 0,265V voltage swing isn't all that useful. The classic two-
transistor emitter-coupled multivibrator has a free collector output,
usually used to drive a third - complementary - transistor as a
saturating switch to provide a rail-to-rail output.

And why use the 2N3904? The BFR92 has much lower internal capacitance
(and a much higher bandwidth) and could probably run with less than a
microamp in either leg. The BFT92 could serve as the saturating
switch.

Well, then go all out and use a BFP620

0.22pF C-E. But be careful, that thing really rocks, ft is 65GHz.

[...]

 

[James Arthur]

On Jul 4, 3:03 am, Jim Thompson wrote:

Not exactly a realistic circuit. Where is the OP going to get 500k
resistors? It isn't an E12 value, or even E24.

And a 0,265V voltage swing isn't all that useful. The classic two-
transistor emitter-coupled multivibrator has a free collector output,
usually used to drive a third - complementary - transistor as a
saturating switch to provide a rail-to-rail output.

And why use the 2N3904? The BFR92 has much lower internal capacitance
(and a much higher bandwidth) and could probably run with less than a
microamp in either leg. The BFT92 could serve as the saturating
switch.

Kvetch, kvetch, kvetch. Jim's circuit is cute; his
bias scheme saves a cap and a resistor over mine.

I'm sure he used 2n3904s because--used carefully--
they're good enough and super-cheap. Don't you
like making neat things from jellybeans? I do.

It's not like it really matters--the OP and his
vague wish list are long gone.

It might be fun to push things farther current-wise
using RF transistors but, why?

Ultimate low-power would dictate a high-Q tank,
probably a crystal and a FET or two.

You could presumably get a decent voltage swing out of Jim's circuit
by adding three more transistors - a long-tailed pair driven from one
of the emitters, and a satuarating switch driven from one of the free
collectors. The tail wouldn't be all that long - only a quarter of a
volt - and you might tap the emitter resistor to trade off voltage
swing for extra DC bias.

I get 1.2v swing out of Jim's circuit with a simple
2uA class-A stage.

Cheers,
James Arthur

 

[krw]

On Thu, 3 Jul 2008 08:58:17 -0700 (PDT), [email protected] wrote:

[snip]

Persistent whining may have worked on your mother but it won't do you
any good here.

I thought that was how you obtained sexual favors ?

I thought that was what he was talking about.

 

[[email protected]]

Kvetch, kvetch, kvetch.  Jim's circuit is cute; his
bias scheme saves a cap and a resistor over mine.

At the expense of any kind of useful output. An oscillator that won't
drive anything isn't all that useful.

I'm sure he used 2n3904s because--used carefully--
they're good enough and super-cheap. Don't you
like making neat things from jellybeans? I do.

Who doesn't? But Jim's effort doesn't really get to neat.

It's not like it really matters--the OP and his
vague wish list are long gone.

It might be fun to push things farther current-wise
using RF transistors but, why?

Lower power dissipation.

Ultimate low-power would dictate a high-Q tank,
probably a crystal and a FET or two.


I get 1.2v swing out of Jim's circuit with a simple
2uA class-A stage.

Biased how? And it might drive ECL and the like, but they aren't low-
power logic.

 

[James Arthur]

At the expense of any kind of useful output. An oscillator that won't
drive anything isn't all that useful.


Who doesn't? But Jim's effort doesn't really get to neat.


Lower power dissipation.


Biased how? And it might drive ECL and the like, but they aren't low-
power logic.

Biased with maximum cheese(iness): 22pF feeds the base
of a 2n3904, 2meg base-to-collector, 470k collector-to-rail.

I goofed twice though: it puts out just under a volt, and draws
3uA. Total circuit draw is still 9uA.

Cheers,
James Arthur

 

[[email protected]]

Biased with maximum cheese(iness): 22pF feeds the base
of a 2n3904, 2meg base-to-collector, 470k collector-to-rail.

I goofed twice though: it puts out just under a volt, and draws
3uA.  Total circuit draw is still 9uA.

At 2V. 25uA at the OP's 5V.

And - now I come to think of it - the BFR92 and BFT92 are jelly bean
parts. Farnell stocks them in buckets. Joerg's 65GHz toy may yet
become another ...

 

[[email protected]]

On Thu, 3 Jul 2008 08:58:17 -0700 (PDT), [email protected] wrote:
[snip]
Persistent whining may have worked on your mother but it won't do you
any good here.
I thought that was how you obtained sexual favors ?
I thought that was what he was talking about.

Yep, From his mother ;-)

   Do you have any proof that he ever had a mother?

My, what a charming company.

 

[[email protected]]

You do get excited about typos - and your spell-checker can find them
for you.

 

[[email protected]]

I'm looking for a schematic for a square wave oscillator which draws
around 10uA, powered by 2 to 5V and oscillates at around 100kHz with a
50% duty cycle. I tried out some schematics around a 4007 but none can
meet all the requirements.

any suggestions here?

regards,
nukeymusic

Has anybody suggestesa 4093 Schmitt trigger NAND yet?
Although that only goes down to 3 V, the input cap i s7.5pF,
and with a single feedback resistor think the charge current will be
low.
Dunno how symmetrical it will be... or how stable.
Maybe there are better suited Schmitt trigger CMOS chips too.

 

[James Arthur]

At 2V. 25uA at the OP's 5V.

I already spec'd a 2v regulated supply--don't make me make it
1.8v and save even more power!

And - now I come to think of it - the BFR92 and BFT92 are jelly bean
parts. Farnell stocks them in buckets. Joerg's 65GHz toy may yet
become another ...

The 2n3904 only shows about 4pF in LTSpice, so there's
really not much to save here with fancy-pants transistors.
I deem it more than good enough for our long-departed OP,
who never really needed any of this anyhow.

Cheers,
James Arthur