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Discussion of precise time and frequency measurement

Re: [time-nuts] 10 MHz -> 16 MHz clock multiplier

M. Simon

Thu, Jan 3, 2013 9:52 AM

I would not use the 4046 these days. It has a dead band around zero phase error.

I would use the 9046 which has no dead band. In addition the integrator supply is a cleaner design. It is a current source.

The data sheet explains it.

http://www.nxp.com/documents/data_sheet/74HCT9046A.pdf

In addition the internal VCO is rated at 17 MHz (typ - 5.5V supply). Depending on how much jitter you can handle a low cost VCXO will give better performance than the on chip osc. Hz/Volt of the VCO is important in keeping jitter down. Smaller is better.

Use the type 2 phase detector. (PC2) If you don't mind the extra chips run the phase detector at between 100KHz and 400KHz. It is a matter of the speed of the technology. 1 MHz is pushing it. It might also be a good idea to bias the internal VCO with a trimpot and let the phase detector just supply the correction. Well it is starting to get complicated.

Simon

Message: 2
Date: Wed, 2 Jan 2013 21:19:16 -0800
From: "WarrenS" warrensjmail-one@yahoo.com
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Subject: Re: [time-nuts] 10 MHz -> 16 MHz clock multiplier
Message-ID: 87417D31224740BFB6BBB320B762E80D@Warcon28Gz
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original

Tom

For simple, cheap, low performance and fast to build with junk box parts,
hard to beat:
What I made long ago for myself (before time-nut days).
I still use it today for low end stuff, and it is all done with standard
74HC DIP parts.
The main IC is a 74HCT4046 Phase lock loop with internal Osc.
The internal osc output is divided by 16 using a 74HC93. The 10MHz ref is
divide by 10 using a 74HC90
The two 1 MHz signals are feed into it's phase comparator. A couple of
resistors and caps and I have a low tech 16 / 8 / 4 / 2 / 1 MHz tracking
ref.
With a couple of tweaks, I got the noise jitter down to a couple of ns as
measured with a scope.
16 MHz is pushing the limits of the internal Osc, but I did not have any
trouble getting there using less than the recommended osc cap.

"What's the simplest way to generate 16 MHz from 10 MHz? This will be for
clocking a microcontroller at 16 MHz given 10 MHz (Cs/Rb/GPSDO).
Low price and low parts count is a goal; jitter is not a concern but
absolute long-term phase coherence is a must.

The ICS525 (as in TAPR Clock-Block) is a good candidate but I was wondering
if there's something cheaper, less functional, and maybe not SSOP. Any
suggestions?

Thanks,
/tvb

Engineering is the art of making what you want from what you can get at a profit.

I would not use the 4046 these days. It has a dead band around zero phase error. I would use the 9046 which has no dead band. In addition the integrator supply is a cleaner design. It is a current source. The data sheet explains it. http://www.nxp.com/documents/data_sheet/74HCT9046A.pdf In addition the internal VCO is rated at 17 MHz (typ - 5.5V supply). Depending on how much jitter you can handle a low cost VCXO will give better performance than the on chip osc. Hz/Volt of the VCO is important in keeping jitter down. Smaller is better. Use the type 2 phase detector. (PC2) If you don't mind the extra chips run the phase detector at between 100KHz and 400KHz. It is a matter of the speed of the technology. 1 MHz is pushing it. It might also be a good idea to bias the internal VCO with a trimpot and let the phase detector just supply the correction. Well it is starting to get complicated. Simon Message: 2 Date: Wed, 2 Jan 2013 21:19:16 -0800 From: "WarrenS" <warrensjmail-one@yahoo.com> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Subject: Re: [time-nuts] 10 MHz -> 16 MHz clock multiplier Message-ID: <87417D31224740BFB6BBB320B762E80D@Warcon28Gz> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Tom For simple, cheap, low performance and fast to build with junk box parts, hard to beat: What I made long ago for myself (before time-nut days). I still use it today for low end stuff, and it is all done with standard 74HC DIP parts. The main IC is a 74HCT4046 Phase lock loop with internal Osc. The internal osc output is divided by 16 using a 74HC93. The 10MHz ref is divide by 10 using a 74HC90 The two 1 MHz signals are feed into it's phase comparator. A couple of resistors and caps and I have a low tech 16 / 8 / 4 / 2 / 1 MHz tracking ref. With a couple of tweaks, I got the noise jitter down to a couple of ns as measured with a scope. 16 MHz is pushing the limits of the internal Osc, but I did not have any trouble getting there using less than the recommended osc cap. ws ******************** "What's the simplest way to generate 16 MHz from 10 MHz? This will be for clocking a microcontroller at 16 MHz given 10 MHz (Cs/Rb/GPSDO). Low price and low parts count is a goal; jitter is not a concern but absolute long-term phase coherence is a must. The ICS525 (as in TAPR Clock-Block) is a good candidate but I was wondering if there's something cheaper, less functional, and maybe not SSOP. Any suggestions? Thanks, /tvb Engineering is the art of making what you want from what you can get at a profit.