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'[OT] Micropower vco needed'
2005\05\02@103741 by KY1K

picon face
I need a low frequency vco that draws very little power. I googled and
found tons of uhf and higher vco's, but they all draw much more power than
I can supply.

I need something that will oscillate between 55 and 65 Khz. It has to draw
microamps of supply current, and I prefer the control voltage range to be
between 1 and 3 volts.

I'd like to have a chip solution if possible.

Any suggestions?

Thanks,

Art


2005\05\02@111356 by Rob Young

picon face


>I need a low frequency vco that draws very little power. I googled and
>found tons of uhf and higher vco's, but they all draw much more power than
>I can supply.
>
> I need something that will oscillate between 55 and 65 Khz. It has to draw
> microamps of supply current, and I prefer the control voltage range to be
> between 1 and 3 volts.
>
> I'd like to have a chip solution if possible.
>
> Any suggestions?
>
> Thanks,
>
> Art




LTC6906 from Linear Technology?  Rset picked as fixed value and instead of
grounding one end, use your control voltage (or probably some buffered and
scaled version).

Rob Young





>
>
> --

2005\05\02@114922 by Mike Harrison

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On Mon, 2 May 2005 10:13:56 -0500, you wrote:

>
>
>>I need a low frequency vco that draws very little power. I googled and
>>found tons of uhf and higher vco's, but they all draw much more power than
>>I can supply.
>>
>> I need something that will oscillate between 55 and 65 Khz. It has to draw
>> microamps of supply current, and I prefer the control voltage range to be
>> between 1 and 3 volts.
>>
>> I'd like to have a chip solution if possible.
>>
>> Any suggestions?
>>
>> Thanks,
>>
>> Art
>
>

I think there are some PLL chips with VCOs in the 4000/74HC series that may be worth looking at.
Also think about making one out of a micropower comparator

2005\05\02@115135 by KY1K

picon face
Thanks Rob,

The current needed to pull the frequency appears to be very small, which
means I don't waste much power feeding the R(set) input.

My next best choice was a low power 555 timer, at around 70 microamps, so
the LT part looks good!

A cmos gate oscillator (4000 series) might draw less power, but I haven't
figured out how to vary the frequency with a voltage input yet.

Regards,

Art


At 11:13 AM 5/2/2005, you wrote:


{Quote hidden}

>>-

2005\05\02@120949 by Dave Tweed

face
flavicon
face
KY1K <spam_OUTky1kTakeThisOuTspampivot.net> wrote:
> I need something that will oscillate between 55 and 65 Khz. It has to draw
> microamps of supply current, and I prefer the control voltage range to be
> between 1 and 3 volts.
>
> I'd like to have a chip solution if possible.

The obvious answer, a CMOS 555, draws 100 uA typical (16 uA for the
internal divider alone).

You can probably do better by building an oscillator based on a micropower
opamp or comparator.

Also, search for low-power "voltage to frequency converters" intended for
use in remote sensors.

This sort of question will probably get better answers under the [EE] tag.

-- Dave Tweed

2005\05\02@133052 by Mark Jordan

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face

       CD4046 maybe?

       Mark Jordan


On 2 May 2005 at 10:37, KY1K wrote:

{Quote hidden}

> --

2005\05\02@135024 by Nigel Duckworth

picon face
Art,

How many microamps max?

What about a PIC12F675 & some code?

Assuming you could clock it slowly enough
to do the job and also be within your
current consumption budget.

Nigel


--{Original Message removed}

2005\05\02@174449 by Peter

picon face

On Mon, 2 May 2005, KY1K wrote:

> Date: Mon, 02 May 2005 10:37:43 -0400
> From: KY1K <.....ky1kKILLspamspam@spam@pivot.net>
> Reply-To: Microcontroller discussion list - Public. <piclistspamKILLspammit.edu>
> To: Microcontroller discussion list - Public. <.....piclistKILLspamspam.....mit.edu>
> Subject: [OT] Micropower vco needed
>
> I need a low frequency vco that draws very little power. I googled and found
> tons of uhf and higher vco's, but they all draw much more power than I can
> supply.
>
> I need something that will oscillate between 55 and 65 Khz. It has to draw
> microamps of supply current, and I prefer the control voltage range to be
> between 1 and 3 volts.
>
> I'd like to have a chip solution if possible.

CMOS4046 PLL (74C4046 etc)

Peter

2005\05\02@181620 by KY1K

picon face
The 74HC4046 requires way to much power, but thanks for the suggestion.

It varies with vendor, but the lowest quiescent current I found was 80 ua,
and that's WITHOUT the VCO running!

It looks like the cmos Shmitt trigger inverter free running oscillator will
use 12-14 ua at 60 Khz. The frequency of the oscillation is changed by
varying the supply voltage. I have a pdf if anyone is interested in the
circuit. It's pretty tough to get any supply current usage less than that:>:

BUT, I'm open to suggestions if anyone has another suggestion:>:

Art


>CMOS4046 PLL (74C4046 etc)


2005\05\02@182936 by Jose Da Silva

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face
On May 2, 2005 02:45 pm, Peter wrote:
> On Mon, 2 May 2005, KY1K wrote:
> > Date: Mon, 02 May 2005 10:37:43 -0400
> > From: KY1K <EraseMEky1kspam_OUTspamTakeThisOuTpivot.net>
> > Reply-To: Microcontroller discussion list - Public.
> > <piclistspamspam_OUTmit.edu> To: Microcontroller discussion list - Public.
> > <@spam@piclistKILLspamspammit.edu> Subject: [OT] Micropower vco needed
> >
> > I need a low frequency vco that draws very little power. I googled
> > and found tons of uhf and higher vco's, but they all draw much more
> > power than I can supply.
> >
> > I need something that will oscillate between 55 and 65 Khz. It has
> > to draw microamps of supply current, and I prefer the control
> > voltage range to be between 1 and 3 volts.
> >
> > I'd like to have a chip solution if possible.
>
> CMOS4046 PLL (74C4046 etc)

At micoamps worth of current, why not use a 16f5x or 12f5x running in RC
mode, then use a varactor as your C.
Something like this:
                               Vcc
                               |
                               Z
               large R                |
Cntrl Voltage>--+--WWW--+---|(--+--PIC RC
               |        |
       large        _        _varactor
       cap.        ^        ^
               |        |
               gnd        gnd
>
> Peter

2005\05\02@183324 by Bob Ammerman

picon face
Maybe just use the VCO portion of a 4066 PLL?

Bob Ammerman
RAm Systems

----- Original Message -----
From: "KY1K" <KILLspamky1kKILLspamspampivot.net>
To: "Microcontroller discussion list - Public." <RemoveMEpiclistTakeThisOuTspammit.edu>
Sent: Monday, May 02, 2005 10:37 AM
Subject: [OT] Micropower vco needed


{Quote hidden}

> --

2005\05\02@193705 by Jinx

face picon face
part 1 509 bytes content-type:text/plain; (decoded 7bit)

> At micoamps worth of current, why not use a 16f5x or 12f5x running
> in RC mode, then use a varactor as your C

Or even use the A2D

What sort of VCO resolution do you want, and how often does it
need to change ?

This two-gate CMOS VCO works OK. I've used it in the past but
have no notes about power consumption. Didn't know there'd be a
test. Values are from the original circuit in ETI 7/82. You may find
that linear characteristics vary between manufacturers



part 2 1155 bytes content-type:image/gif; (decode)


part 3 35 bytes content-type:text/plain; charset="us-ascii"
(decoded 7bit)

2005\05\02@203028 by KY1K

picon face
You're the second one to suggest a PIC digital solution.

I think it's not practical because you would have to clock the PIC at 10
Mhz (or higher) in order to get small increments at the 55 Khz output.
Doesn't the clock frequency limit the smallest length of time that the PIC
can be driven high?

For instance, a 36 Khz clock would mean I could not run the vco at any
frequency less than 36 Khz....

The application is for a piezotransformer based photomultiplier tube
(cockcroft-walton) power supply, so digital jumps in the output frequency
will make steps in the output of the poser supply instead of nice slow and
smooth increments from an analog solution.

This is probably a case where analog is better because the digital solution
requires a very high clock frequency, thus more supply current is needed.

Am I in error?

Thanks,

Art



At 05:30 PM 5/2/2005, you wrote:
{Quote hidden}

>

2005\05\02@225235 by Jose Da Silva

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face
On May 2, 2005 05:30 pm, KY1K wrote:
> You're the second one to suggest a PIC digital solution.

...well, looks like I'm in good company to suggest a PIC, hehehe!

> I think it's not practical because you would have to clock the PIC at
> 10 Mhz (or higher) in order to get small increments at the 55 Khz
> output. Doesn't the clock frequency limit the smallest length of time
> that the PIC can be driven high?

...wrong direction, this is a digital attempt at an analog solution.
I'm suggesting to modify the actual running frequency using a varactor.

Run the PIC at External RC speed of about 220 to 240kHz and tap the PIC
OSC2 output for your frequency out of 55...60kHz.

At the OSC1, to achieve RC speed of about 220kHz...240kHz, you need to
calculate the appropriate values of R and C required for your PIC to
run at 240kHz operation. The unmarked cap is a large C to block DC
voltage between your varactor DC circuit and your PIC.
Some varactors will run at about 300pF when at about 1...3v, so you may
need to add 1 or more in parallel, or modify your large cap, so that
the series capacitance only tunes the appropriate range.

These are just numbers out of the blue for an imaginary 240kHz operation
(assuming T=RC, or 1/240kHz=27k x 150pF), so you need to find the
correct numbers for correct operation.

> >                               Vcc
> >                                |
> >                                Z = 27Kohm
> >                large R large C |
> >Cntrl Voltage>--+--WWW--+---|(--+--PIC (OSC1)=220..240kHz
> >                |       |       |
> >        large   _       _var    _
> >        cap.    ^       ^       ^ = 150pF
> >                |       |       |
> >               gnd     gnd     gnd

2005\05\02@225808 by Jose Da Silva

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face
On May 2, 2005 04:35 pm, Jinx wrote:
> > At micoamps worth of current, why not use a 16f5x or 12f5x running
> > in RC mode, then use a varactor as your C
>
> Or even use the A2D

a varactor is an upside down diode with a large capacitance and the
capacitance varies with applied voltage.

> This two-gate CMOS VCO works OK. I've used it in the past but
> have no notes about power consumption. Didn't know there'd be a
> test. Values are from the original circuit in ETI 7/82. You may find
> that linear characteristics vary between manufacturers

Hi jinx, I don't think the circuit in the picture applies here.
A VCO is a Voltage Controlled Oscillator in which a voltage will modify
the frequency of operation.

2005\05\03@014550 by Jinx

face picon face
> Hi jinx, I don't think the circuit in the picture applies here.
> A VCO is a Voltage Controlled Oscillator in which a voltage
> will modify the frequency of operation

And that's exactly what that circuit does

2005\05\03@014558 by Jinx

face picon face


> You're the second one to suggest a PIC digital solution.
>
> I think it's not practical because you would have to clock the
> PIC at 10Mhz (or higher) in order to get small increments at
> the 55 Khz output.

Why didn't you say what you actually needed in the first place ?

2005\05\03@023441 by Russell McMahon

face
flavicon
face
>> You're the second one to suggest a PIC digital solution.

>> I think it's not practical because you would have to clock the
>> PIC at 10Mhz (or higher) in order to get small increments at
>> the 55 Khz output.

> Why didn't you say what you actually needed in the first place ?

You have the right number of letters but your name is spelled wrong.
And I doubt that you have the requisite temperament. Stick to you day
job.  :-)

I think the original spec was reasonably clear
Viz

>I need a low frequency vco that draws very little power. ...
> I need something that will oscillate between 55 and 65 Khz. It has
> to draw
> microamps of supply current, and I prefer the control voltage range
> to be
> between 1 and 3 volts.

The implication (to me anyway) is that he wants an oscillator which is
tuneable in a reasonably smooth manner between 55 & 65 KHz by a 1 to 3
volt signal. The (or a ) problem is that threads such as this wander
all over (often quite usefully) and the original spec is forgotten.



       RM

2005\05\03@023915 by Jose Da Silva

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face
On May 2, 2005 10:43 pm, Jinx wrote:
> > Hi jinx, I don't think the circuit in the picture applies here.
> > A VCO is a Voltage Controlled Oscillator in which a voltage
> > will modify the frequency of operation
>
> And that's exactly what that circuit does

In that case, it's far easier & cheaper than a pic circuit.  :-)

2005\05\03@082701 by KY1K

picon face

>
>The implication (to me anyway) is that he wants an oscillator which is
>tuneable in a reasonably smooth manner between 55 & 65 KHz by a 1 to 3
>volt signal. The (or a ) problem is that threads such as this wander all
>over (often quite usefully) and the original spec is forgotten.

Hey All,

Sorry to cause such a ruckus.............

But, the above statement is exactly correct.

I did read the PIC based solution and understand that I was mistaken
regarding the clock frequency and the output frequency relationship. I went
over the end requirements for my design and cannot see the need for a PIC
in any other function. If I needed a PIC for other functions, I'd probably
use the PIC solution though.

Thanks to all of you who made suggestions and comments.

Art


2005\05\03@095844 by Jinx

face picon face
> I think the original spec was reasonably clear
> Viz
>
> >I need a low frequency vco that draws very little power. ...
> > I need something that will oscillate between 55 and 65 Khz. It has
> > to draw microamps of supply current, and I prefer the control
> > voltage range to be between 1 and 3 volts.
>
> The implication (to me anyway) is that he wants an oscillator which is
> tuneable in a reasonably smooth manner between 55 & 65 KHz by a
> 1 to 3 volt signal

That might not necessarily have been the requirement. There was
no mention of infinite (ie analogue) variability or even whether there
were any steps between 55kHz and 65kHz, or over what time
period. I didn't mean to sound snippy in my reply but you know
how often we play 20 Questions

Apart from the PIC and 40xx there may not be alternatives at
that power level

2005\05\03@134747 by Peter

picon face

On Mon, 2 May 2005, KY1K wrote:

> Date: Mon, 02 May 2005 18:15:38 -0400
> From: KY1K <ky1kEraseMEspam.....pivot.net>
> Reply-To: Microcontroller discussion list - Public. <EraseMEpiclistspammit.edu>
> To: Microcontroller discussion list - Public. <RemoveMEpiclistEraseMEspamEraseMEmit.edu>
> Subject: Re: [OT] Micropower vco needed
>
> The 74HC4046 requires way to much power, but thanks for the suggestion.
>
> It varies with vendor, but the lowest quiescent current I found was 80 ua,
> and that's WITHOUT the VCO running!

I said 74C4046 or CMOS4046, not HC. Quiescent should be 5-10nA w/o osc
running (CD4046B 5V 20C). Another chip that was designed with low power
oscillation in mind was the 4047. CD4046 needs 70uW at 10kHz (14uA @ 5V)
and it runs down to 3V. The 4047 can run on 20uW (4uA) at 5V and 1kHz.
If you reduce the supply to 3V you can get them 50% lower probably.

Peter

2005\05\03@150143 by Jose Da Silva

flavicon
face
On May 3, 2005 06:58 am, Jinx wrote:
{Quote hidden}

He can look at the circuit used in a television, 55kHz to 65kHz is more
or less the same speeds used for the horizontal trace on a television,
and those circuits certainly need to "syncronize" to another signal.
All he needs to do is recalculate values so that his circuit uses
miniscule amounts of current versus a regular horizontal trace.

2005\05\04@070523 by Alan B. Pearce

face picon face
>I did read the PIC based solution and understand that I was mistaken
>regarding the clock frequency and the output frequency relationship. I went
>over the end requirements for my design and cannot see the need for a PIC
>in any other function. If I needed a PIC for other functions, I'd probably
>use the PIC solution though.
>
>Thanks to all of you who made suggestions and comments.

Well, if you got real sneaky you could have the PIC generate a PWM signal
that you filter to control its own VCO frequency. Then you could have a
serial interface to the PIC to send commands to change the frequency. Then
your control program just needs to know how to fiddle the baud rate
generation to keep listening to the serial data to receive commands  to
change the PWM signal.

Sounds like it should all fit into a 12F6xx ;)))))))))))0

2005\05\04@072812 by KY1K

picon face

>>
>>It varies with vendor, but the lowest quiescent current I found was 80
>>ua, and that's WITHOUT the VCO running!
>
>I said 74C4046 or CMOS4046, not HC. Quiescent should be 5-10nA w/o osc
>running (CD4046B 5V 20C). Another chip that was designed with low power
>oscillation in mind was the 4047. CD4046 needs 70uW at 10kHz (14uA @ 5V)
>and it runs down to 3V. The 4047 can run on 20uW (4uA) at 5V and 1kHz. If
>you reduce the supply to 3V you can get them 50% lower probably.

Thanks Peter,

I did not realize the HC used more power than the C version. I'll search
one out and see what the specs are. I actually like the 4046 as it had a
comparator in the package, which would come in handy for my design too.

GL to all.

Art


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