PLL suggestions
Hi All,
We've got a project going on where we need a 125MHz clock that should be
locked to 10MHz. I'm considering an on board 10MHz oscillator and
external 10MHz input to utilize an external standard to lock the 125MHz
which would PLL a 125MHz source.
The 125MHz becomes a reference for 3.125Ghz, as well as logic running at
125Mhz. (Currently this system is running on small 125MHz TCXO.)
Basically we need a reasonably clean 125MHz signal, but locked to 10Mhz
for frequency reference.
We've identified a few VCXO's that seem to be low noise and are small
enough. The 10Mhz is easy enough. However my stumbling block is a simple
PLL.
What I'm looking for is a simple, small PLL chip. Something with
external analog loop filter components to allow easy tweaking would be
preferred.
In my perfect world, this chip would be a COTS part, with pin strappable
divider configuration or similarly simple hardware configuration. An OTP
device would work as well, as would one with it's own memory and
external programmer. If necessary a small PIC or similar could be used
to configure the PLL, but that's one chip which would be nice to avoid.
Smaller compact package SMT parts are fine. This is going on a board
with lots of SMT components, leadless flat pack devices and BGA's, so
smaller is better.
If any of you have any suggestions, I'd appreciate it.
Happy new year!
Dan
You need to determine your requirements for phase
noise. You also need to coordinate this PLL with
the phase noise of the 3.125 GHz PLL, which will
need its own VCO.
The best VCXO's I have found are from Abracon,
COTS in distribution (DigiKey, etc) for only
about $25. Lucky for you that 125 MHz is a
standard frequency for them. At 3.125 GHz there are several
vendors such as Z-comm to browse. You need
to find one with 3.125 GHz output frequency and then
it needs to be low phase noise. May not be
available. It's just the luck of the draw
as to what they choose to make.
Any PLL chip with a divider and on board phase
detector will give only mediocre performance
(which may be good enough for you). And it
will require a microcontroller to load the
gazillion registers onboard (no strapping). For
high performance, you need a conventional
multiplier from 10 MHz to, say, 120 MHz and
then mix down to 5 MHz and use a mixer as
a phase detector. You can divide the 10 MHz
by 2 using a 74AC74.
You decide: performance vs cost/simplicity.
Rick N6RK
On 12/31/2019 8:01 AM, Dan Kemppainen wrote:
Hi All,
We've got a project going on where we need a 125MHz clock that should be
locked to 10MHz. I'm considering an on board 10MHz oscillator and
external 10MHz input to utilize an external standard to lock the 125MHz
which would PLL a 125MHz source.
We've identified a few VCXO's that seem to be low noise and are small
enough. The 10Mhz is easy enough. However my stumbling block is a simple
PLL.
What I'm looking for is a simple, small PLL chip. Something with
external analog loop filter components to allow easy tweaking would be
preferred.
Dan there are numbers of small PLL chips that should work well and are
really reasonable to use. Its just unclear to me if they will hit the lower
noise performance you may need. I am thinking of the Silicon Labs family
but analog devices and others have very nice chips these days also. Good
luck
Paul.
On Tue, Dec 31, 2019 at 11:15 AM Dan Kemppainen dan@irtelemetrics.com
wrote:
Hi All,
We've got a project going on where we need a 125MHz clock that should be
locked to 10MHz. I'm considering an on board 10MHz oscillator and
external 10MHz input to utilize an external standard to lock the 125MHz
which would PLL a 125MHz source.
The 125MHz becomes a reference for 3.125Ghz, as well as logic running at
125Mhz. (Currently this system is running on small 125MHz TCXO.)
Basically we need a reasonably clean 125MHz signal, but locked to 10Mhz
for frequency reference.
We've identified a few VCXO's that seem to be low noise and are small
enough. The 10Mhz is easy enough. However my stumbling block is a simple
PLL.
What I'm looking for is a simple, small PLL chip. Something with
external analog loop filter components to allow easy tweaking would be
preferred.
In my perfect world, this chip would be a COTS part, with pin strappable
divider configuration or similarly simple hardware configuration. An OTP
device would work as well, as would one with it's own memory and
external programmer. If necessary a small PIC or similar could be used
to configure the PLL, but that's one chip which would be nice to avoid.
Smaller compact package SMT parts are fine. This is going on a board
with lots of SMT components, leadless flat pack devices and BGA's, so
smaller is better.
If any of you have any suggestions, I'd appreciate it.
Happy new year!
Dan
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Don't forget the "regenerative" frequency divider concept, either. At some
point you'll
need to do some division, and these things seem to have a rep for better
phase noise
performance than logic-based dividers.
Dana
On Tue, Dec 31, 2019 at 10:15 AM Dan Kemppainen dan@irtelemetrics.com
wrote:
Hi All,
We've got a project going on where we need a 125MHz clock that should be
locked to 10MHz. I'm considering an on board 10MHz oscillator and
external 10MHz input to utilize an external standard to lock the 125MHz
which would PLL a 125MHz source.
The 125MHz becomes a reference for 3.125Ghz, as well as logic running at
125Mhz. (Currently this system is running on small 125MHz TCXO.)
Basically we need a reasonably clean 125MHz signal, but locked to 10Mhz
for frequency reference.
We've identified a few VCXO's that seem to be low noise and are small
enough. The 10Mhz is easy enough. However my stumbling block is a simple
PLL.
What I'm looking for is a simple, small PLL chip. Something with
external analog loop filter components to allow easy tweaking would be
preferred.
In my perfect world, this chip would be a COTS part, with pin strappable
divider configuration or similarly simple hardware configuration. An OTP
device would work as well, as would one with it's own memory and
external programmer. If necessary a small PIC or similar could be used
to configure the PLL, but that's one chip which would be nice to avoid.
Smaller compact package SMT parts are fine. This is going on a board
with lots of SMT components, leadless flat pack devices and BGA's, so
smaller is better.
If any of you have any suggestions, I'd appreciate it.
Happy new year!
Dan
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On 12/31/19 8:45 AM, Richard (Rick) Karlquist wrote:
You need to determine your requirements for phase
noise. You also need to coordinate this PLL with
the phase noise of the 3.125 GHz PLL, which will
need its own VCO.
The best VCXO's I have found are from Abracon,
COTS in distribution (DigiKey, etc) for only
about $25.
+1 for Abracon - excellent phase noise performance for off the shelf
devices that are cheap and in stock
Lucky for you that 125 MHz is a
standard frequency for them. At 3.125 GHz there are several
vendors such as Z-comm to browse. You need
to find one with 3.125 GHz output frequency and then
it needs to be low phase noise. May not be
available. It's just the luck of the draw
as to what they choose to make.
Any PLL chip with a divider and on board phase
detector will give only mediocre performance
(which may be good enough for you). And it
will require a microcontroller to load the
gazillion registers onboard (no strapping).
This is the problem these days. A parallel load PLL is almost unheard
of today.
You might look at the (formerly Hittite) HMC parts at Analog Devices -
low phase noise on chip VCOs, and/or low noise divider that can divide
your 3.125 down. Hittite used to have a fixed Divide By N that could do
your 3125 to 125 (divide by 25).
A quick glance at AD's website looks like the HMC705 can do divide by 5,
so you could cascade a couple of these. It doesn't look like the "divide
by anything up to 56" part still exists, at least that will take 3.125.
You might also find a HMC part with a VCO to cover your range.
If you're doing a one-off, there are eval boards with SMA connectors,
etc. available.
For
high performance, you need a conventional
multiplier from 10 MHz to, say, 120 MHz and
then mix down to 5 MHz and use a mixer as
a phase detector. You can divide the 10 MHz
by 2 using a 74AC74.
You decide: performance vs cost/simplicity.
Rick N6RK
On 12/31/2019 8:01 AM, Dan Kemppainen wrote:
Hi All,
We've got a project going on where we need a 125MHz clock that should
be locked to 10MHz. I'm considering an on board 10MHz oscillator and
external 10MHz input to utilize an external standard to lock the
125MHz which would PLL a 125MHz source.
We've identified a few VCXO's that seem to be low noise and are small
enough. The 10Mhz is easy enough. However my stumbling block is a
simple PLL.
What I'm looking for is a simple, small PLL chip. Something with
external analog loop filter components to allow easy tweaking would be
preferred.
time-nuts mailing list -- time-nuts@lists.febo.com
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and follow the instructions there.
Hi
If you are talking about a conventional PLL, the days of pin programable single chip
devices are long gone. Indeed they didn’t last long “back in the day”. The most common
answer is to hook up a cheap micro to shoot the registers. You could also do it with an
FPGA. A lot depends on what is already in the system.
With logic, GHz, and a PLL involved, isolation to keep crud down will be part of the
answer …..
Bob
On Dec 31, 2019, at 11:01 AM, Dan Kemppainen dan@irtelemetrics.com wrote:
Hi All,
We've got a project going on where we need a 125MHz clock that should be locked to 10MHz. I'm considering an on board 10MHz oscillator and external 10MHz input to utilize an external standard to lock the 125MHz which would PLL a 125MHz source.
The 125MHz becomes a reference for 3.125Ghz, as well as logic running at 125Mhz. (Currently this system is running on small 125MHz TCXO.) Basically we need a reasonably clean 125MHz signal, but locked to 10Mhz for frequency reference.
We've identified a few VCXO's that seem to be low noise and are small enough. The 10Mhz is easy enough. However my stumbling block is a simple PLL.
What I'm looking for is a simple, small PLL chip. Something with external analog loop filter components to allow easy tweaking would be preferred.
In my perfect world, this chip would be a COTS part, with pin strappable divider configuration or similarly simple hardware configuration. An OTP device would work as well, as would one with it's own memory and external programmer. If necessary a small PIC or similar could be used to configure the PLL, but that's one chip which would be nice to avoid.
Smaller compact package SMT parts are fine. This is going on a board with lots of SMT components, leadless flat pack devices and BGA's, so smaller is better.
If any of you have any suggestions, I'd appreciate it.
Happy new year!
Dan
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and follow the instructions there.
Hi Dan,
This is possible with the Broadcom BCM54210SE or BCM54220SE. Ethernet PHY with built in jitter cleaner. External loop filter, 10MHz input is possible, 125MHz output locked to 10MHz is possible but not documented. The Ethernet PHYs will also be locked to the 10MHz input and it has HW 1 step 1588 support
I was one of the designers of this part email me off list if you need more info.
Jay On Tuesday, December 31, 2019, 10:15:26 AM CST, Dan Kemppainen dan@irtelemetrics.com wrote:
Hi All,
We've got a project going on where we need a 125MHz clock that should be
locked to 10MHz. I'm considering an on board 10MHz oscillator and
external 10MHz input to utilize an external standard to lock the 125MHz
which would PLL a 125MHz source.
The 125MHz becomes a reference for 3.125Ghz, as well as logic running at
125Mhz. (Currently this system is running on small 125MHz TCXO.)
Basically we need a reasonably clean 125MHz signal, but locked to 10Mhz
for frequency reference.
We've identified a few VCXO's that seem to be low noise and are small
enough. The 10Mhz is easy enough. However my stumbling block is a simple
PLL.
What I'm looking for is a simple, small PLL chip. Something with
external analog loop filter components to allow easy tweaking would be
preferred.
In my perfect world, this chip would be a COTS part, with pin strappable
divider configuration or similarly simple hardware configuration. An OTP
device would work as well, as would one with it's own memory and
external programmer. If necessary a small PIC or similar could be used
to configure the PLL, but that's one chip which would be nice to avoid.
Smaller compact package SMT parts are fine. This is going on a board
with lots of SMT components, leadless flat pack devices and BGA's, so
smaller is better.
If any of you have any suggestions, I'd appreciate it.
Happy new year!
Dan
time-nuts mailing list -- time-nuts@lists.febo.com
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and follow the instructions there.