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Frequency divider (divide by 100)

S

sck0006

Jan 1, 1970
0
I need to make a phase stable divide by 100 frequency divider. The
input signal is 10Mhz, and I need 100kHz output. Phase shift isn't
important, as long as it is stable. Should a 74HC390 do the job?

If so, the 10MHz input is around 2-3VRMS, and I need to get a TTL
level square wave to input to the ripple counter, correct? Any
suggestions about how to do that?

Is there another EASY way to go about doing this (i.e., no assembly
language, I'm pretty poor at writing code).

If it helps, I'm trying to check the accuracy of the variable phase
portion of a 3325b. In the manual it calls for another signal
generator at 100kHz, and measure time interval between the uut and
other std. The problem I'm having is none of our signal geneartors go
down that low, besides the 3325b. I'd like to just divide the 10MHz
reference and use it as the other signal, but frequency must be exact,
and there can't be any phase drift. There should be no frequency
error (negligable would be more proper) with a divider, should there?

All suggestions appreciated.

Thanks,
Steve
 
P

petrus bitbyter

Jan 1, 1970
0
I need to make a phase stable divide by 100 frequency divider. The
input signal is 10Mhz, and I need 100kHz output. Phase shift isn't
important, as long as it is stable. Should a 74HC390 do the job?

If so, the 10MHz input is around 2-3VRMS, and I need to get a TTL
level square wave to input to the ripple counter, correct? Any
suggestions about how to do that?

Is there another EASY way to go about doing this (i.e., no assembly
language, I'm pretty poor at writing code).

If it helps, I'm trying to check the accuracy of the variable phase
portion of a 3325b. In the manual it calls for another signal
generator at 100kHz, and measure time interval between the uut and
other std. The problem I'm having is none of our signal geneartors go
down that low, besides the 3325b. I'd like to just divide the 10MHz
reference and use it as the other signal, but frequency must be exact,
and there can't be any phase drift. There should be no frequency
error (negligable would be more proper) with a divider, should there?

All suggestions appreciated.

Thanks,
Steve

A 74HC390 will do, but you'll need a high speed comparator to obtain a good
logic clock signal. Consider an NE529 or a MAX975. A circuit like this will
have no drift but you may encounter jitter. This will mainly depend on the
quality of your input signal but may be influenced by the comparator
circuit.

petrus bitbyter
 
C

Chris

Jan 1, 1970
0
petrus said:
A 74HC390 will do, but you'll need a high speed comparator to obtain a good
logic clock signal. Consider an NE529 or a MAX975. A circuit like this will
have no drift but you may encounter jitter. This will mainly depend on the
quality of your input signal but may be influenced by the comparator
circuit.

petrus bitbyter

And if you're using a single supply comparator like the MAX975, you may
want to use the HP3325B auxillary Sync Output (square wave output, HI
=1.2V, LO >= 0.2V), and be sure to terminate using a 50 ohm resistor. That square wave has great rise and fall times for your comparator conversion to TTL and then the HC390 (remember, /2 last if you want a 100KHz square wave).

Don't worry, it's digital -- there will be _no_ frequency error from
the /100 section. Your propagation delays should be consistent too.

Good luck
Chris
 
D

David L. Jones

Jan 1, 1970
0
sck0006 said:
I need to make a phase stable divide by 100 frequency divider. The
input signal is 10Mhz, and I need 100kHz output. Phase shift isn't
important, as long as it is stable. Should a 74HC390 do the job?

Yes indeed.
If so, the 10MHz input is around 2-3VRMS, and I need to get a TTL
level square wave to input to the ripple counter, correct? Any
suggestions about how to do that?

Correct. You need a comparator to give you a square wave for your 390.
I've done exactly that with a MAX4212, but there are plenty of others
that will work fine.
Is there another EASY way to go about doing this (i.e., no assembly
language, I'm pretty poor at writing code).

You already have the easiest way.
If it helps, I'm trying to check the accuracy of the variable phase
portion of a 3325b. In the manual it calls for another signal
generator at 100kHz, and measure time interval between the uut and
other std. The problem I'm having is none of our signal geneartors go
down that low, besides the 3325b. I'd like to just divide the 10MHz
reference and use it as the other signal, but frequency must be exact,
and there can't be any phase drift. There should be no frequency
error (negligable would be more proper) with a divider, should there?

Correct.
There should be no frequency error, no phase error, and no drift error.
You will however get a small amount of jitter on top of what your 10MHz
source signal already has, but that won't be an issue in your case.

I have done this to characterise the long term drift of a DTCXO
oscillator module using a 10MHz sine wave Rubidium frequency standard.
Email me if you want the circuit.

Dave :)
 
S

sck0006

Jan 1, 1970
0
And if you're using a single supply comparator like the MAX975, you may
want to use the HP3325B auxillary Sync Output (square wave output, HI

I haven't checked, but will the sync output vary when you change the
phase on the 3325b? If it doesn't, then I don't need the circuit at
all, and just can compare phase of the sync to the output. I'll have
to check tomorrow.
 
S

sck0006

Jan 1, 1970
0
I haven't checked, but will the sync output vary when you change the
phase on the 3325b? If it doesn't, then I don't need the circuit at
all, and just can compare phase of the sync to the output. I'll have
to check tomorrow.
Just checked today, the sync varies in phase w/ the output signal, so I
can't use it for the reference phase. Thanks for the idea though. The
reference signal is a 10MHz sine wave from an HP 58540A gps receiver,
do you think this will be adequate to drive a comparator for a stable
square wave out?

Thanks for all your help everyone.

Steve

<clip>
 
C

Chris

Jan 1, 1970
0
sck0006 said:
Just checked today, the sync varies in phase w/ the output signal, so I
can't use it for the reference phase. Thanks for the idea though. The
reference signal is a 10MHz sine wave from an HP 58540A gps receiver,
do you think this will be adequate to drive a comparator for a stable
square wave out?

Thanks for all your help everyone.

Steve

<clip>

Hi, Steve. I'm not familiar with the HP58540A -- you might want to
glance at the manual.

Petrus' original idea is a good one. Just make sure you terminate the
signal properly, and try it. If you get clean logic transistions at
the comparator output, you should be done. If not, please feel free to
post back.

Good luck
Chris
 
S

sck0006

Jan 1, 1970
0
Chris wrote:
<clip
Hi, Steve. I'm not familiar with the HP58540A -- you might want to
glance at the manual.

Petrus' original idea is a good one. Just make sure you terminate the
signal properly, and try it. If you get clean logic transistions at
the comparator output, you should be done. If not, please feel free to
post back.

Good luck
Chris

I'm having troubles. I want to use this whole circuit at a single +5V
supply to simplify things. The only two comparators I have handy are
an LM219D and an LM360. It appears (though I haven't actually
experimented), that the LM360 won't run off that low a voltage on a
single supply (the datasheet states minimum -4.5/+4.5). The LM219D
seems to run fine off the single 5V, but I can't get good logic output
above around 250-300kHz. At 10MHz, I can't get anything out besides
either pegged at +5 or 0 w/ 10MHz noise (based on how I bias the
comparator/input amplitude, etc...). Is this based on the fact that
it's only rated for 80ns at +-15V, and that I'm using a sine wave
input? Is there a better comparator that's readily avaliable in small
quantities (<5), in a dip package, will run off of single +5V, and work
well at 10MHz? The MAX975 looks nice, but I really don't want to get
into surface mount parts. This is just a one time project I'm building
on veraboard. I suppose I could implement a positive/negative supply,
but I was just trying to keep it to minimum parts and maximum
simplicity.

Thanks for all your help, and I will clarify anything if necessary.

Steve
 
C

Chris

Jan 1, 1970
0
sck0006 said:
I'm having troubles. I want to use this whole circuit at a single +5V
supply to simplify things. The only two comparators I have handy are
an LM219D and an LM360. It appears (though I haven't actually
experimented), that the LM360 won't run off that low a voltage on a
single supply (the datasheet states minimum -4.5/+4.5). The LM219D
seems to run fine off the single 5V, but I can't get good logic output
above around 250-300kHz. At 10MHz, I can't get anything out besides
either pegged at +5 or 0 w/ 10MHz noise (based on how I bias the
comparator/input amplitude, etc...). Is this based on the fact that
it's only rated for 80ns at +-15V, and that I'm using a sine wave
input? Is there a better comparator that's readily avaliable in small
quantities (<5), in a dip package, will run off of single +5V, and work
well at 10MHz? The MAX975 looks nice, but I really don't want to get
into surface mount parts. This is just a one time project I'm building
on veraboard. I suppose I could implement a positive/negative supply,
but I was just trying to keep it to minimum parts and maximum
simplicity.

Thanks for all your help, and I will clarify anything if necessary.

Steve

Hi, Steve. Could you describe a little more about your situation?
There are many ways to square up a 2-3VRMS sine wave into a stable
digital logic signal, particularly if you're not too picky about 50%
duty cycle.

For one thing, it's fairly easy to do the level translation with a
diode, transistor, and a couple of resistors if you have a low
impedance signal source (view in fixed font or M$ Notepad):

|
| VCC
| +
| |
| |
| .-.
| 1K| |
| |
| '-
| |
| o--------->
| |
| ___ |/
| o------o->|-o-|___|-| 2N4401
| | | 220 |>
| 50 ohm| | |
| .-. .-. |
| | | | |220 |
| | | | | |
| '-' '-' |
| | | |
| | | |
| o------o----o---------o
| |
| ===
| GND
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

You may have to tweak the resistors a bit to be sure you get a good
1-0-1-0 logic level here. This depends on the amplitude of your signal
(you may need an additional gain stage if the level varies by a lot.
Now if you had a veritable panoply of HC ICs available, you would then
just use a 74HC14 to give you a squared off logic signal for your
comparators. The 15ns propagation delay is sufficient for a 10MHz
pulse.

But actually, that probably isn't necessary. As long as your clock
pulse width exceeds 30ns (check!), you should be OK. The HC390 is
fairly forgiving on clock rise and fall times, at least on this time
scale.

Good luck
Chris
 
C

Chris

Jan 1, 1970
0
Chris said:
|
| VCC
| +
| |
| |
| .-.
| 1K| |
| |
| '-
| |
| o--------->
| |
| ___ |/
| o------o->|-o-|___|-| 2N4401
| | | 220 |>
| 50 ohm| | |
| .-. .-. |
| | | | |220 |
| | | | | |
| '-' '-' |
| | | |
| | | |
| o------o----o---------o
| |
| ===
| GND
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Oh, yes -- diode 1N914 or equivalent signal diode -- don't use a 1N4001
here.

Chris
 
S

sck0006

Jan 1, 1970
0
I'm probably getting confusing at this point. I'll try to clairfy. I
have a 10MHz oscillator reference (the GPS receiver) feeding into a
5087a distribution amplifier which is our main timebase for all the
equipment. Therefore I can adjust the amplitude of the signal
relitavely easily, but I would rather design the circuit to input a
range of around 2-3VRMS, that way I can use any of the outputs from the
amplifier because they are all adjusted within that range at this
point, and we change around our equipment from different outputs often.
I need to convert this 10MHz signal into a 100kHz signal. The shape
of the 100kHz signal isn't necessarily important, as long as it is
stable (no phase or frequency drift). That's pretty much it. I was
going to use the HC390 for the divider, of course, and that part seems
fine. I'm just working on the 10MHz TTL clock. That circuit you have
looks promising. I had just input the sine directly into the
comparator with the inverting input at a level of around 1VDC, and the
sine wave of a level of appx 4VPK, (8VP-P). I'm not much of a design
engineer, as you can tell, I mostly work on repair & cal of avionics.

Thanks for all your help, I'll build up that circuit tonight and post
back.

Steve
 
D

David L. Jones

Jan 1, 1970
0
sck0006 said:
Chris wrote:
<clip

I'm having troubles. I want to use this whole circuit at a single +5V
supply to simplify things. The only two comparators I have handy are
an LM219D and an LM360. It appears (though I haven't actually
experimented), that the LM360 won't run off that low a voltage on a
single supply (the datasheet states minimum -4.5/+4.5). The LM219D
seems to run fine off the single 5V, but I can't get good logic output
above around 250-300kHz. At 10MHz, I can't get anything out besides
either pegged at +5 or 0 w/ 10MHz noise (based on how I bias the
comparator/input amplitude, etc...). Is this based on the fact that
it's only rated for 80ns at +-15V, and that I'm using a sine wave
input? Is there a better comparator that's readily avaliable in small
quantities (<5), in a dip package, will run off of single +5V, and work
well at 10MHz? The MAX975 looks nice, but I really don't want to get
into surface mount parts. This is just a one time project I'm building
on veraboard. I suppose I could implement a positive/negative supply,
but I was just trying to keep it to minimum parts and maximum
simplicity.

Thanks for all your help, and I will clarify anything if necessary.

Steve

Use the Maxim parametric guide on the website to find a suitable device
rated for single rail operation, and then order some free samples ;-)
Start here: http://para.maxim-ic.com/index.mvp?tree=comparators&ln=en

Dave :)
 
J

John Fields

Jan 1, 1970
0
I'm probably getting confusing at this point. I'll try to clairfy. I
have a 10MHz oscillator reference (the GPS receiver) feeding into a
5087a distribution amplifier which is our main timebase for all the
equipment. Therefore I can adjust the amplitude of the signal
relitavely easily, but I would rather design the circuit to input a
range of around 2-3VRMS, that way I can use any of the outputs from the
amplifier because they are all adjusted within that range at this
point, and we change around our equipment from different outputs often.
I need to convert this 10MHz signal into a 100kHz signal. The shape
of the 100kHz signal isn't necessarily important, as long as it is
stable (no phase or frequency drift). That's pretty much it. I was
going to use the HC390 for the divider, of course, and that part seems
fine. I'm just working on the 10MHz TTL clock. That circuit you have
looks promising. I had just input the sine directly into the
comparator with the inverting input at a level of around 1VDC, and the
sine wave of a level of appx 4VPK, (8VP-P). I'm not much of a design
engineer, as you can tell, I mostly work on repair & cal of avionics.

Thanks for all your help, I'll build up that circuit tonight and post
back.

Steve

---
From:

http://groups.google.com/support/bin/answer.py?answer=12348&topic=250

"Summarize what you're following up.

When you click "Reply" under "show options" to follow up an existing
article, Google Groups includes the full article in quotes, with the
cursor at the top of the article. Tempting though it is to just
start
typing your message, please STOP and do two things first.
Look at the quoted text and remove parts that are irrelevant.
Then, go to the BOTTOM of the article and start typing there.
Doing this makes it much easier for your readers to get through your
post. They'll have a reminder of the relevant text before your
comment, but won't have to re-read the entire article.
And if your reply appears on a site before the original article
does,
they'll get the gist of what you're talking about."
 
S

sck0006

Jan 1, 1970
0
---
From:

http://groups.google.com/support/bin/answer.py?answer=12348&topic=250

"Summarize what you're following up.

When you click "Reply" under "show options" to follow up an existing
article, Google Groups includes the full article in quotes, with the
cursor at the top of the article. Tempting though it is to just
start
typing your message, please STOP and do two things first.
Look at the quoted text and remove parts that are irrelevant.
Then, go to the BOTTOM of the article and start typing there.
Doing this makes it much easier for your readers to get through your
post. They'll have a reminder of the relevant text before your
comment, but won't have to re-read the entire article.
And if your reply appears on a site before the original article
does,
they'll get the gist of what you're talking about."

Sorry, I suppose I cut too much text out (all of it in this case,
oops) and the original conversation was lost. Apologies to all for
the confusion.

Steve
 
S

sck0006

Jan 1, 1970
0
Use the Maxim parametric guide on the website to find a suitable device
rated for single rail operation, and then order some free samples ;-)
Start here: http://para.maxim-ic.com/index.mvp?tree=comparators&ln=en

Dave :)

Good idea, I guess I'm just not too well versed at desigining circuits
and selecting products. I'm more used to building pre-engineered
circuits, but I really would like to expand my knowledge and
experience. Thanks for the advice.

Steve
 
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