In message 1225454799-1347767280-cardhu_decombobulator_blackberry.rim.net-1901
834519-@b27.c1.bise6.blackberry, li...@lazygranch.com writes:
The PWM DAC should have perfect differential linearity, which I
believe is all that matters in this application. (That and no missing
codes.) Not so when
gandal...@aol.com said:
When some other form of external control is used, such as a DAC output for
example, it's not uncommon to find the voltage reference output left
disconnected and the control circuit fed from an alternative supply.
On the other hand, many DACs need an external
Hal Murray wrote:
d...@montana.com said:
Michael: Actually implementing a 16 bit DAC to its 1-bit minimum resolution
will be headache enough. You will gain a real education in good grounding
practice, shielding, power supply stability and noise, and other Murphy
intrusion. A 32 bit DAC
On 09/15/2012 12:08 AM, Hal Murray wrote:
d...@montana.com said:
Michael: Actually implementing a 16 bit DAC to its 1-bit minimum resolution
will be headache enough. You will gain a real education in good grounding
practice, shielding, power supply stability and noise, and other Murphy
Second the comments on implementing a 16 bit DAC. You need separate
analogue/digital grounds, superb voltage references, and lots of attempts
to get a good design that actually uses the L.S. bit (rather than losing it
in the noise).
What you can do is use a second DAC to offset the 16 bit DAC.
-nuts-boun...@febo.com
Date: Sun, 16 Sep 2012 12:00:55
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO control loops and correcting quantization
Greetings nuts,
I've been working on a simple GPSDO as a starting point for further
experimentation. I'm using a STM32 microcontroller running at 72MHz as
the heart, with the input capture peripheral comparing the phase of the
pulses-per-second and a 16 bit PWM DAC to drive the VFC. It's all
Hi M.
welcome to the world of GPSDO optimization, one thing you will find is
that there never is a time when there is no chance to improve something :)
On the 1PPS sawtooth correction, the usual convention is for the following
1PPS.
The easiest thing to do rather than trying to guess
On Fri, Sep 14, 2012 at 11:21 AM, Michael Tharp
g...@partiallystapled.com wrote:
Finally, do people think a 16 bit DAC is adequate or should I consider
building a 32-bit one? I looked at a few designs when putting this together
but decided to keep it simple until things were up and running.
Also you need a super ultra fantastic voltage reference for a 32bit DAC.
Anyway, yes, in my GPSDO the controller has 3 levels: at startup is fast,
then slow and then very slow. The levels trigger when the precision
estimate is 10E-9 and 10E-11. If you have a resolution of 10nS then take 10
Azelio Boriani wrote:
Also you need a super ultra fantastic voltage reference for a 32bit DAC.
Not really, the reference only needs to have low noise and good short
term stability.
Long term drift in the reference voltage will be corrected by the
feedback loop.
Anyway, yes, in my GPSDO
Yes, you are right: but actually I have a 2.5nS simple time interval
counter in the FPGA and the only way to go beyond is the average. The
sophisticated way would be to implement a tapped delay line or vernier
delay line time-to-digital converter in a bigger FPGA than the XC3S50. And,
yes, I have
Michael: Actually implementing a 16 bit DAC to its 1-bit minimum
resolution will be headache enough. You will gain a real education in
good grounding practice, shielding, power supply stability and noise,
and other Murphy intrusion. A 32 bit DAC IMHO, is impossible, and that's
the name of that
-- Forwarded message --
From: Don Latham d...@montana.com
Date: Fri, Sep 14, 2012 at 2:01 PM
Subject: Re: [time-nuts] GPSDO control loops and correcting quantization error
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Michael: Actually implementing
On 09/14/2012 05:31 PM, Chris Albertson wrote:
Michael: Actually implementing a 16 bit DAC to its 1-bit minimum
resolution will be headache enough. You will gain a real education in
good grounding practice, shielding, power supply stability and noise,
and other Murphy intrusion. A 32 bit DAC
d...@montana.com said:
Michael: Actually implementing a 16 bit DAC to its 1-bit minimum resolution
will be headache enough. You will gain a real education in good grounding
practice, shielding, power supply stability and noise, and other Murphy
intrusion. A 32 bit DAC IMHO, is impossible, and
Hello all,
Most voltage controlled XOs have a voltage reference output. Is it necessary
for the DAC output / frequency control input, to track this voltage reference
output?
Thank You
Don O'Connor
___
time-nuts mailing list --
Hi Don,
I don't know if I've misunderstood your question, but as I understand it
the voltage reference output is a fixed voltage from an internal regulator
that can then be used as the supply to an external control circuit.
For example, it could be used as the feed voltage for a variable
If it is a reference then tracking is not the correct term: it shouldn't
move. If it is a reference then can be used for the DAC.
On Sat, Sep 15, 2012 at 12:10 AM, Don Oconnor eg...@wowway.com wrote:
Hello all,
Most voltage controlled XOs have a voltage reference output. Is it
necessary
Nigel,
Yes, you understood and answered the question.
Thank you
Don O
I don't know if I've misunderstood your question, but as I understand it
the voltage reference output is a fixed voltage from an internal regulator
that can then be used as the supply to an external control circuit.
On Fri, 14 Sep 2012 15:08:53 -0700, Hal Murray
hmur...@megapathdsl.net wrote:
d...@montana.com said:
Michael: Actually implementing a 16 bit DAC to its 1-bit minimum resolution
will be headache enough. You will gain a real education in good grounding
practice, shielding, power supply stability
My 2.5nS TIC? Very simple: a 400MHz counter start-stop gated with the two
signal to compare. I have published here the VHDL code for it few months
ago. Really nothing new but simple and useful for a 35-40nS GPSDO PPS
output from an OCXO. The Rb PPS wondering is actually under evaluation
against
Hi
Very few VCXO's have reference outputs. Some OCXO's have reference outputs. The
gotcha there is the oven current. You can easily get multiple mV sort of
changes in the OCXO ground voltage as the oven current cycles over a fairly
narrow range. That significantly impacts the usefulness of
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